# How to test Rad. Fan control Module, or have fans run on high



## jsbaker (Jan 30, 2009)

Pusrant to my other thread I think i have determined my rad. fans are only running on low. Before I go and drop the $$ for a new control module can anyone tell me how to test the module or make the fans run on high. Or for that matter can someone tell me what tells them to kick into high. They come one when the a/c is on but on on low and I have never heard them on high and living in Texas it should have happened by now.
Car in question is a 2002 Jetta wagon, 1.8t. Unfortunately I don't think the module on my MKIII is the same so I can't just do a swap test.
If there is an easy way to make them run on high all the time that would also work for now till I can get a new module, provided that is the problem.


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## Andaloons (Apr 16, 2004)

*Re: How to test Rad. Fan control Module, or have fans run on high (jsbaker)*









1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
5. If the fans run as described in steps 3 and 4, it indicates that the cooling fans and circuits are running properly and the thermo switch is faulty.
6. If the fans do not operate with the thermo switch bypassed, check for voltage at the red wire of the thermo switch electrical connector. There should be battery voltage. 
7. If voltage is not present check the large cooling fuses in the engine compartment fuse holder and the No. 16 fuse in the passenger compartment fuse box. If the fuses are OK, the problem lies in the wiring harness, the fan control module or the coolant temperature sensor.
8. Check the wiring for open or short circuits. The fan control module can only be diagnosed as faulty through process of elimination.


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## BassNotes (Mar 16, 2005)

Good info. Bump.


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## Krissrock (Sep 10, 2005)

having this issue with my TT. The fans only seem to come on occasionally when the car has been turned off...But never come on when the car is running hot and still running....So i know the fans work, but didn't know what else to look into... 

Thanks for the info...:thumbup:


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## Andaloons (Apr 16, 2004)

I was wondering were this thread was hiding. I'm glad it was helpful! 

:beer:


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## builtvw (Sep 20, 2009)

bump


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## nismodrifter (Apr 2, 2004)

Excellent thread.

I have disconnected the wire from the radiator temperature sensor.............and the fans CONTINUE running. wtf? I am guessing fan control module is gone. Will be performing the tests as described above tomorrow and see what happens.


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## radlynx (Jan 4, 2007)

I have this problem but kind of different. my auxiliary fan for the radiator is not turning on when I turn on the a/c on all the speed settings. but, i could see the a/c compressor turn on. would this be a fan control module problem? the part# i checked for my car, this is what I will need, 1J0919506K. 

any help will be great. thank you.



nismodrifter said:


> Excellent thread.
> 
> I have disconnected the wire from the radiator temperature sensor.............and the fans CONTINUE running. wtf? I am guessing fan control module is gone. Will be performing the tests as described above tomorrow and see what happens.


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## radlynx (Jan 4, 2007)

Thank you for the info. I used this to test the low speed and high speed last night. ended up that the low speed does not turn on on both of them. I am finally concluding that the 2 of my auxiliary fan is bad. 
A/C smaller fan part# 1C0959455C (female connector)
Engine bigger fan part# 1J0959455S (male connector)




radlynx said:


> I have this problem but kind of different. my auxiliary fan for the radiator is not turning on when I turn on the a/c on all the speed settings. but, i could see the a/c compressor turn on. would this be a fan control module problem? the part# i checked for my car, this is what I will need, 1J0919506K.
> 
> any help will be great. thank you.


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## radlynx (Jan 4, 2007)

have you tested your fan if it's running on high per the instruction here?



jsbaker said:


> Pusrant to my other thread I think i have determined my rad. fans are only running on low. Before I go and drop the $$ for a new control module can anyone tell me how to test the module or make the fans run on high. Or for that matter can someone tell me what tells them to kick into high. They come one when the a/c is on but on on low and I have never heard them on high and living in Texas it should have happened by now.
> Car in question is a 2002 Jetta wagon, 1.8t. Unfortunately I don't think the module on my MKIII is the same so I can't just do a swap test.
> If there is an easy way to make them run on high all the time that would also work for now till I can get a new module, provided that is the problem.


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## radlynx (Jan 4, 2007)

*How to Test the Fan Control Module*

"On this vehicle, the cooling fan and A/C compressor operation are controlled by the J293 fan control module, which is usually located in the driver's front corner of the engine compartment on the lower frame rail. The J293 module has both a 14-pin connector identified as the T14 connector in Volkswagen wiring diagrams and a four-pin connector identified as the T4a connector. To diagnose this system, starting on the T14 connector: 

1) Start and idle the vehicle. Select "A/C on" at maximum cooling and "blower on" at high speed. 

2) Check for 12 volts at the T14 connector pin No. 8 (T14/8). This 12-volt signal comes from the A/C switch and requires both cooling fans on at low speed and compressor activation. 

3) Check for 12 volts at pin T14/9. This voltage is a switched ignition source and will have 12 volts when the ignition is in the "on" position. 

4) Check for 12 volts at pin T14/4. This is a constant battery source and should read 12 volts at all times from fuse S16. 

5) Check for a good ground at pin T14/6. 

6) Check for 12 volts at all times at the four-pin connector, T4a pins T4a/1 and T4a/3 from fuses S164 and S180, respectively. 

7) Turn off the ignition. Remove the T14 connector and check for continuity between pins T14/14 and T14/5 on harness side to ensure proper operation of the F38 ambient temperature switch. Continuity must be present if the ambient air temperature is above 32 degrees Fahrenheit. Reconnect the T14 connector and restart the vehicle. 

8) Check pin T14/2 using a duty cycle meter. If the refrigerant charge in the system is normal, about 30 percent to 35 percent duty should be indicated at pin T14/2 without the compressor engaged. The duty cycle signal is supplied by the G65 pressure sensor in response to system pressure changes. A duty cycle above 90 percent or below 20 percent will command the compressor off. 

9) Check for an 11-volt reference voltage at pin T14/3. The reference voltage originates in the J293 fan control module and can be grounded by |the power control module (PCM) under certain circumstances (typically wide open throttle or vehicle overheat conditions) to turn the A/C compressor off. 

If zero volts are present, the PCM is commanding "compressor off" or the wiring harness is shorted to ground. Raise vehicle idle speed above 2500 rpm and observe compressor operation and voltage at pin T14/3. If the voltage at pin T14/3 returns to 11 volts with the idle speed above 2500 rpm and compressor operation resumes, then a throttle basic setting procedure is needed and must be performed with a factory-compatible, by-directional scan tool. Note: A loss of throttle basic settings will keep the compressor from activating. 

If all previous tests have passed, check the T14 connector pin T14/10 for 12 volts. This pin is the output signal to the compressor clutch coil. If all the other tests have passed and there is no voltage at pin T14/10, this indicates a faulty fan control module." 

I got this from this link... http://www.gti-vr6.net/wiki/index.php?title=Fault_diagnosis_in_the_Fan_Control_Module



radlynx said:


> have you tested your fan if it's running on high per the instruction here?


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## bink_420 (Jul 11, 2008)

Trying this out tomorrow.....hope it solves my problem:facepalm:


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## turbojunky (May 1, 2011)

*valuable info, thank u for the thread!!*

Ive had overheating issues, and fans not working, along with my AC coming out warm! I started by changing out the coolant temp sensor, and than tested the fans which were dead! Since than Ive replaced coolant temp sensor which turned my AC cold again, but fans still dont kick in when overheating unless I turn AC on?! They have been cutting in n out and NOW after reading this thread, Im hoping to get to the bottom of this!!

Thanks again for such a detailed thread!!


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## DrKnowone (Mar 22, 2009)

Can't forget this thread


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## matty675 (Oct 2, 2011)

is it possible for the fcm to fail intermittently? how does the cts affect the fans?


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## MK420TH92 (Nov 3, 2011)

does anyone have a pic where to fan module is? Im pretty sure mine needs replacement.


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## Andaloons (Apr 16, 2004)

The FCM is basically underneath the battery. You can't miss it!

It looks like this:


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## MK420TH92 (Nov 3, 2011)

Andaloons said:


> The FCM is basically underneath the battery. You can't miss it!
> 
> It looks like this:



:thumbup::thumbup::thumbup::thumbup::thumbup::beer:


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## Slimjimmn (Apr 8, 2006)

fyi, in 8 years I have never replaced a Fan module on a mk4.

I have though replaced probably 20 fans, and probably 20-30 fuse/relay pannels on top the battery related to radiator fan issues.


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## FTMFW (Jan 1, 2008)

I only needed to replace mine because when I got rear ended it pushed me into the tow hitch of the Eurovan in front of me. Guess where it hit...


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## MK420TH92 (Nov 3, 2011)

Slimjimmn said:


> fyi, in 8 years I have never replaced a Fan module on a mk4.
> 
> I have though replaced probably 20 fans, and probably 20-30 fuse/relay pannels on top the battery related to radiator fan issues.



When my car over heats it gets to like temp 220+ and fans don't come on. I guess ill try to replace the fuse/relay pannels first.


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## Slimjimmn (Apr 8, 2006)

no reason to replace it unless its burned or melted.


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## kay05GLi (Feb 18, 2011)

I was one of the many people looking for this part and the details really are fairly vague as to where this item is (atleast directly under the battery doesn't quite sound detailed enough for me) So here we go. Disconnect the battery terminals, then remove the battery. After that there is the "crib" or plastic box the battery sits in. It has 4 bolts holding it in, remove these bolts and pull it out. This is where it should be and is however what people forget to mention is it is under the metal tray that the "crib" was bolted into. Once you get the four bolts out and have the plastic peice out if you look a little closer twords the front bumper and a little to the left you will notice two bolts (mine were a silver pewterish color). these two bolts hold the module in place and the module itself is directly under these bolts. Just undo the bolts the module will slide right out (it does have a little piece that slides into a sleeve but its not clipped in thank god) and then undo the two plugs in the back of it. I hope this helps I should have taken a picture but inforutnatly I was dog sick while working on this so it didn't happen. As stated just look for those two small bolts a little cadycorner from the battery box and you are golden. 

-Also my problem that replacing this fixed. My fans completely died on me thursday morning, I put in a new fan assembly and coolant sensor on friday and when I turned on the ignition the fans kicked on instantly.... both of them even though the A/C was off. thinking this was strange I still started the car and they continued to run. turned off the car and what do ya know...... they continued to run for 45 min till I just disconnected the negative battery terminal. I checked the sensor and fuse tricks posted on here and all that was left was the module which turned out to be the electrical monster I was looking for. I assume it fried my fan motors out too but can't be certain. 

Also fyi to get to this part the front bumper does not need to be removed. I didn't read it on VWVortex but some other site google so graciously sent me too had a "VW Tech" stating to get to the module the whole front assembly needed to be removed. He was an idiot. 

Good luck with your issues! Happy dubbing! :thumbup:


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## bink_420 (Jul 11, 2008)

I've had an issue with my fans for as long as i can remember. They seem to NEVER want to turn on. I removed my ac last year because i left my ac on when i wasn't in the car for 10 minutes and it burnt out my compressor due to over heating (go figure). I've replaced my cts to a green top 2+ years ago, main fan, my FCM, AND the thermal switch on the rad, now they STILLLLLLL don't turn on, i'm almost ready to throw a switch on them but still want to do a bit of digging before i resort to that. Can ANYBODY give some insight? i absolutely have no idea what else to do.


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## Andaloons (Apr 16, 2004)

bink_420 said:


> I've had an issue with my fans for as long as i can remember. They seem to NEVER want to turn on. I removed my ac last year because i left my ac on when i wasn't in the car for 10 minutes and it burnt out my compressor due to over heating (go figure). I've replaced my cts to a green top 2+ years ago, main fan, my FCM, AND the thermal switch on the rad, now they STILLLLLLL don't turn on, i'm almost ready to throw a switch on them but still want to do a bit of digging before i resort to that. Can ANYBODY give some insight? i absolutely have no idea what else to do.


Did you go through the tests in post #11? That should narrow down your problem. Also there is a good video with similar test here.


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## matty675 (Oct 2, 2011)

all of these parts need to be replaced with OEM parts, if not that is quite possibly the issue


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## forcefedjetta (Aug 14, 2003)

I noticed my cooling fan relay was bad when the ac would blow warm in traffic the fan was not turning on then a few weeks later I was having a beer with a friend in the driveway when the fan came on when the engine was cold so I whacked relay with a screw driver and fan turned off


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## xXGti2006Xx (Feb 14, 2006)

where is this relay?


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## Slimjimmn (Apr 8, 2006)

its the fan control module:sly:


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## mk4boost (Jul 31, 2010)

gonna need this :thumbup:


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## Taran (Jun 5, 2010)

Bump. Summer is coming and this always a hot topic :laugh:


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## 02337 (May 12, 2009)

Thanks for the reminder, ever since my coolant flange cracked my fans have had issues. System is completely burped. Thinking tomorrow ill just switch to a Manuel system with a switch as its going to make life easier and I drive an hour to work all highway. Still it'd be nice not to have to worry in traffic about overheating.

Looking for a simple diagram. Switch, Low/high off


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## akrazyassho (Jul 18, 2010)

This maybe a silly question but how do you test for these voltages on the T14 connector while its plugged in and the car is running (as outline in post #11)?


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## Slimjimmn (Apr 8, 2006)

just check the resistance of the fan, if its more then a couple ohm 2-4 (say 80ohm) the fan is shorted. 

you can check power with a t-pin tool.


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## BassNotes (Mar 16, 2005)

Slimjimmn said:


> just check the resistance of the fan, if its more then a couple ohm 2-4 (say 80ohm) the fan is shorted.
> 
> you can check power with a t-pin tool.


A short would be an abnormally low resistance, actually.


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## Slimjimmn (Apr 8, 2006)

BassNotes said:


> A short would be an abnormally low resistance, actually.


Lol...:facepalm:


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## BassNotes (Mar 16, 2005)

Don't feel bad, it's a common misunderstanding. Some people even call an open circuit a short.


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## Slimjimmn (Apr 8, 2006)

lol... 

short to positive will cause high resistance, you are adding a load to a circuit
Short to ground before a load will cause low resistance.
a shorted field winding in an electric motor (fan) will cause high resistance reading and blow fuses.


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## K20017 (Nov 14, 2007)

Slimjimmn said:


> lol...
> 
> short to positive will cause high resistance, you are adding a load to a circuit
> Short to ground before a load will cause low resistance.
> a shorted field winding in an electric motor (fan) will cause high resistance reading and blow fuses.


A short circuit will cause a low resistance, whether it is to ground or positive, it is the same thing. The electricity is taking the shortest/least path of resistance. 

Unless the circuit is battling some corrosion, in this case, it would be a high resistance.


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## BassNotes (Mar 16, 2005)

Slimjimmn said:


> lol...
> 
> short to positive will cause high resistance, you are adding a load to a circuit
> Short to ground before a load will cause low resistance.
> a shorted field winding in an electric motor (fan) will cause high resistance reading and blow fuses.


This might help: http://en.wikipedia.org/wiki/Ohm's_law


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## akrazyassho (Jul 18, 2010)

Anyway I tested all the pins as outlined in post #11, got correct voltages out of everything. Now tested the voltage at the clutch and got 7.6 volts. Now first question is shouldn't it read 12ish volts at the a/c clutch to engauge. Second question, assuming there's the right pressure in the system, can I wire a switch w/ a fuse on it to run the clutch when I need a/c (and if so what size fuse should I place on it)??


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## Slimjimmn (Apr 8, 2006)

measure the resistance of the clutch coil.
should be 1-3ohm. if its high then the clutch coil is bad and you need a compressor.

also you can have a short to b+ or short to ground.


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## Achilles (May 8, 2002)

On my '01 New Beetle, the fans don't come on when the car gets up to temperature (being a NB I can't tell exactly what the temperature was but I'd assume the low speed would come on some time after the blue temp idiot light goes out), and the fans don't come on when the AC is selected either. 

Following the troubleshooting steps, I can turn on the low speed fans via connecting terminals 1 & 2 of the thermo switch plug. But when I connect to terminals 2 & 3, the high speed fans do not come on. I can turn the high speed on by jumpering the large terminals '30a' and '2' on the plug for the Fan Control Module. 

I'm guessing that my problem lies in my FCM being bad, as I come from the MK3 world where they go bad quite often, but I'm unsure as Step 4 of the directions below, doesn't test out 'ok' on my car. Any advice? 



Andaloons said:


> 1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
> 2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
> 3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
> 4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
> ...


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## Achilles (May 8, 2002)

Replaced the FCM with another from the junkyard. I can now jumper the fans on via the temperature sensor plug. I believe the second half of my problem is a bad temp sensor.

For the mean time, I jumpered the high speed fan as that is key-on powered, so simple to wire up for temporary.


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## Slimjimmn (Apr 8, 2006)

be careful with that key on powerup. It will melt those fans in a hurry on a hot muggy day. :thumbup:


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## Marcus_Aurelius (Mar 1, 2012)

Good thread :thumbup:


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## heart_crafter (Jun 21, 2012)

*I'm going jump in this thread also *

I bought a NB couple weeks ago... made a thread for it...

Thought i'd add an image here i posted in my other thread...
Pic taken from under driver-side, just beside the bottom end of radiator.

FCM (Fan Control Module)









My fan is dead; doesn't even run when a/c is turned on, also no cool air from a/c (maybe no freon/leak somewhere).
I'll post more when I'm done testing what i can  (novice in repair, first car in the garage like that)


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## Popssracer21 (Jul 18, 2012)

*AC issues tied to Fans*

Hi folks, got a slightly different problem to add to this, see if anyone can suggest anything.

Since I've gotten the car, (over 100,000 miles ago) the AC cuts out sporadically, ONLY when I'm not moving, and seemingly only in traffic. The AC has always worked when I'm moving, even relatively slowly. About 20,000 miles ago I dug into it and found that my second cooling fan was dead, and replaced it. This did not fix the issue, although both fans run now when theyre supposed to, for the most part (see below). This is where it gets complicated. I emptied and recharged the AC system with exactly the right amount of freon, etc, the other day, and let it idle in my driveway to see if i could reproduce the problem. I had the AC gauges hooked up to both high and low side and, eventually, this is what happened:

1. AC operating normally, both fans runnin good.
2. Both fans spin down and stop
3. AC continues to run, but the high side pressure shoots up and up and up
4. AC compressor kicks out, presumably due to high side pressure
5. Fans kick back in, high side pressure drops, compressor kicks back in, return to step 2, repeat over and over.

I have not done the tests listed in this thread yet, mainly because I cant get it to do this on command under testing circumstances. I can reproduce it flawlessly in traffic for some reason, everytime i stop driving, the ac cuts out. The car never overheats, however. It will cut out at every traffic stop on my hour drive home, but when i pull into the driveway and sit there, it almost never does it for some reason. This is the part thats really puzzling me. Given these symptoms, however, if I can get it to do it again in the driveway, which of the leads do I need to test? Is there a seperate signal for "fans on cause the ac is on" than "fans on cause its hot/without AC on". If i turn the AC off and am idling on a hot day, the fans work flawlessly. They only seem to kick on and off when I have the AC on.

It might also help to note that it does this even at the first stoplight 100 yards down from my work, so its not like it only does it when everything gets full-on hot


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## PixieStix5spd (Dec 15, 2007)

I think this is what you're looking for.



> 9) Check for an 11-volt reference voltage at pin T14/3. The reference voltage originates in the J293 fan control module and can be grounded by |the power control module (PCM) under certain circumstances (typically wide open throttle or vehicle overheat conditions) to turn the A/C compressor off.
> 
> If zero volts are present, the PCM is commanding "compressor off" or the wiring harness is shorted to ground. Raise vehicle idle speed above 2500 rpm and observe compressor operation and voltage at pin T14/3. If the voltage at pin T14/3 returns to 11 volts with the idle speed above 2500 rpm and compressor operation resumes, then a throttle basic setting procedure is needed and must be performed with a factory-compatible, by-directional scan tool. Note: A loss of throttle basic settings will keep the compressor from activating.


I imagine you could always just try doing the Throttle Body Adaptation and see if it solves the problem.


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## Popssracer21 (Jul 18, 2012)

*Fan Controller*



PixieStix5spd said:


> I think this is what you're looking for.
> 
> 
> 
> I imagine you could always just try doing the Throttle Body Adaptation and see if it solves the problem.


Well, I installed the new fan controller that arrived on Saturday, we'll see if that fixed the problem. The fans seemed to turn on full strength when I turned the AC on full, but the real test will be today when its hottest on my commute home. Normally, stopped in traffic when its hottest is the only time it consistently used to kick out, so I am really hoping that it will not.

Edit: During my lunch drive around town in heavy traffic, it did NOT kick out at all. This isnt completely conclusive, the proof still lies in the drive home test, but its looking good.

Edit again: Replacing the fan controller has fixed the problem! Rejoice! After 100,000 miles, actually getting off my butt and diagnosing the thing properly has fixed it! Many thanks to the folks who posted the testing stuff at the beginning of this thread!


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## Klegraefe (Jul 21, 2012)

If ur fans aint working, take them out and lightly tap on the motor with a hammer then try connecting power to it again, this work for mee..


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## heart_crafter (Jun 21, 2012)

*fan is back online!*

came out that it was the fuse box at the top of the battery! 
Fuse was fine... but the place where fuse goes in was kind of melted... 
I scrubbed out some plastic from there, then sanded of the terminals and fuse... and voila! 

How i figured it out? 
-Connected volt meter to the thermo switch (red to red wire, striped wire to ground) 
-I was getting about 40mV in the switch. 
-Wiggled all the wires, while wiggling the fuses on top of the battery I saw the voltage jump. 
-I wasn't able to see the melted plastic until i took out the fuse. 
-Took out the fuse... and fixed it! 
-This is how i figured it out! 

melted fuse box. 









check out my thread... repairing a wreck(first time)... 

Thanks


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## paveltv (Nov 2, 2012)

*How to reconnect electrical connector to fan motor?*

Hi everyone, 
My problem is a little different, I'm afraid it's much simpler but I don't know how to test for this.
I just recently disconnected the radiator fan of my 1997 Jetta GLS but I forgot how to reconnect the 3 loose cables (all the same color) that attach to the connector (it looks like type I from the picture) in the fan motor. Is there a way to find out in which order they connect to terminals 1, 2 and 3 without having to turn on the car and wait until the system activates the fan?
I'd really appreciate any help. Thanks!

PTV




Andaloons said:


> 1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
> 2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
> 3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
> 4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
> ...


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## henwilsch (Nov 28, 2012)

*Fan Controle Module*

Hi, firstly I would like to thank everybody for their input on this thread, it helped me to solve my problem. It turnned out to be the fan controle module. My car use the *1J0 919 506 M*. After getting a quote on a new one (+/- $220) I decided to open mine to see if it was fixable. To my surprize inside is 2x Relays 4x Diodes and 6x resistors. These spares would cost +/- $10 from a electronic spares shop.

This unit is totaly repairable by anybody with a little elecrical/electronic know how. Mine had a broken wire on the slow speed(fan) relay coil. I resoldered it and problem solved. I took some photos of the opened unit if somebody is interested.

Regards

Henry


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## groggory (Apr 21, 2003)

henwilsch said:


> Hi, firstly I would like to thank everybody for their input on this thread, it helped me to solve my problem. It turnned out to be the fan controle module. My car use the *1J0 919 506 M*. After getting a quote on a new one (+/- $220) I decided to open mine to see if it was fixable. To my surprize inside is 2x Relays 4x Diodes and 6x resistors. These spares would cost +/- $10 from a electronic spares shop.
> 
> This unit is totaly repairable by anybody with a little elecrical/electronic know how. Mine had a broken wire on the slow speed(fan) relay coil. I resoldered it and problem solved. I took some photos of the opened unit if somebody is interested.
> 
> ...


Post up the pics and do a FAQ topic on how to repair a fan control module. This would save lots of people some money!


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## rickysantana (Nov 29, 2009)

.


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## ZachSav (Nov 12, 2011)

My fan was stone dead. Picked up another from the junkyard, dead too. So I decided to take it apart and see what broke.

two magnets are frozen in place so with a little lude they slide free and make contact again.

fixed.


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## iammclovin804 (Jun 3, 2013)

Didn't want to start a new thread since this one is already out there. My fans don't work unless I jump the pins on the connectors (thermo switch, fcm). I just replaced the thermo switch and the fcm today and still no success. These fans haven't worked since I bought the car 5 months ago and I would like them to so I can get the compressor to kick on and get some a/c. Any ideas on what I should test next?


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## ZachSav (Nov 12, 2011)

iammclovin804 said:


> Didn't want to start a new thread since this one is already out there. My fans don't work unless I jump the pins on the connectors (thermo switch, fcm). I just replaced the thermo switch and the fcm today and still no success. These fans haven't worked since I bought the car 5 months ago and I would like them to so I can get the compressor to kick on and get some a/c. Any ideas on what I should test next?


Did you go through the 8 tests above? Its rare, but possible both fans are dead


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## iammclovin804 (Jun 3, 2013)

ZachSav said:


> Did you go through the 8 tests above? Its rare, but possible both fans are dead


Both fans work fine on high and low when jumped. They just aren't turning on on their own. And yes I tested everything. Is there any other sensor that controls them besides the thermo switch or fcm?


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## dennisgli (May 17, 2003)

iammclovin804 said:


> Is there any other sensor that controls them besides the thermo switch or fcm?


The FCM isn't a sensor - it's basically a set of relays for the fans and compressor clutch. The fans should come on at low speed when you turn on the air conditioning.


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## iammclovin804 (Jun 3, 2013)

dennisgli said:


> The FCM isn't a sensor - it's basically a set of relays for the fans and compressor clutch. The fans should come on at low speed when you turn on the air conditioning.


They don't. If the compressor is bad would that prevent the fans from coming on at all? Also, I don't know if this matters but I can hear the secondary coolant pump working when the car is off. It stops when I unplug the fcm.


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## dennisgli (May 17, 2003)

iammclovin804 said:


> If the compressor is bad would that prevent the fans from coming on at all?


I don't think so - but it wouldn't hurt to test it just so you know what all works and what doesn't.



iammclovin804 said:


> My fans don't work unless I jump the pins on the connectors (thermo switch, fcm). I just replaced the thermo switch and the fcm today and still no success.


But let's back up a minute - you replaced the thermal switch and the fans still don't run? Are you sure that the car is getting hot enough to run the fans?


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## iammclovin804 (Jun 3, 2013)

dennisgli said:


> I don't think so - but it wouldn't hurt to test it just so you know what all works and what doesn't.
> 
> 
> 
> But let's back up a minute - you replaced the thermal switch and the fans still don't run? Are you sure that the car is getting hot enough to run the fans?


Temp gets up to 190 on the gauge. I also tested the plug going to the compressor and with key on/engine off ac on, I got 11 volts. 
I'm tempted to just wire up a 3 way switch for the fans at this point because all of my pins get proper current at proper times but the fans just won't come on.


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## iammclovin804 (Jun 3, 2013)

Read on another thread that the a/c pressure switch controls compressor operation. 
Attached pic to show what mine looks like. 









So my switch has 3 wires but my harness has 4. Looks like I need to buy a new switch with pigtail.


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## dennisgli (May 17, 2003)

iammclovin804 said:


> Temp gets up to 190 on the gauge.


That doesn't mean that the radiator fans should be running at that point.



iammclovin804 said:


> I also tested the plug going to the compressor and with key on/engine off ac on, I got 11 volts.


So you're saying that you're getting power to the compressor when the engine isn't running? Does the clutch engage?



iammclovin804 said:


> I'm tempted to just wire up a 3 way switch for the fans at this point because all of my pins get proper current at proper times but the fans just won't come on.


What do you mean by "proper current"? How are you measuring it? If current is flowing through the fans and they aren't spinning they are bound up and they should be blowing fuses. I think there is something wrong with how you are testing things.


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## iammclovin804 (Jun 3, 2013)

dennisgli said:


> That doesn't mean that the radiator fans should be running at that point.
> 
> 
> 
> ...


No everything tested out. I found the pigtail for the ac pressure switch in the door panel. Soldered that back up, then bought the proper switch. Fans work as they should now.


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## Jhu-D (Apr 7, 2008)

Andaloons said:


> <IMG SRC="http://img.photobucket.com/albums/v315/Andaloons/general%20photos/DSCF3532.jpg" BORDER="0"><p>1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.<br>2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.<br>3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.<br>4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.<br>5. If the fans run as described in steps 3 and 4, it indicates that the cooling fans and circuits are running properly and the thermo switch is faulty.<br>6. If the fans do not operate with the thermo switch bypassed, check for voltage at the red wire of the thermo switch electrical connector. There should be battery voltage. <br>7. If voltage is not present check the large cooling fuses in the engine compartment fuse holder and the No. 16 fuse in the passenger compartment fuse box. If the fuses are OK, the problem lies in the wiring harness, the fan control module or the coolant temperature sensor.<br>8. Check the wiring for open or short circuits. The fan control module can only be diagnosed as faulty through process of elimination.





radlynx said:


> "On this vehicle, the cooling fan and A/C compressor operation are controlled by the J293 fan control module, which is usually located in the driver's front corner of the engine compartment on the lower frame rail. The J293 module has both a 14-pin connector identified as the T14 connector in Volkswagen wiring diagrams and a four-pin connector identified as the T4a connector. To diagnose this system, starting on the T14 connector:
> 
> 1) Start and idle the vehicle. Select "A/C on" at maximum cooling and "blower on" at high speed.
> 
> ...



Hi there... I did not perform all the test as described but maybe you could tell me if my problem is related. I own a *2004 Jetta / 2.0 Engine* which is overheating as my fans are not working except when the A/C is working but will however overheating after 15-20 minutes of driving and the A/C is blowing hot air. I also noticed that the fans never run on High Speed during this time. The Temperature indicator on the Instrument panel reaches the 3/4 marks (100 C) and sometimes close to the Red Limit marks (120 C)

I had made the test (Originally Posted by Andaloons / Thank you man...) on the Fan Thermo Switch Electrical connector (Jumped Terminal 1 and 2 : Both fans run at Low Speed / Jumped Terminal 2 and 3 : Both fans run at High Speed) and later replaced the *Fan Thermo Switch* and the *Cooling Temperature Sensor* but that did not resolve the problem.

But I noticed that the fans are running (While the engine is running) when I pulled out the Fuse No. 16 out of the Passenger Compartment Fuse Box. They are still running even when I shut down the engine until I put the fuse back. 

Could it be the Fan Control Module or is the A/C switch can be involved ?

Please someone give me some advice... Thanks !!!


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## K C (Jul 26, 2014)

First post here and I am having a very odd problem. I did the, "A4 Coolant Fan testing, MANUAL Air Conditioning" tests and when I test the fans through the thermoswitch, the low speed works when pins 1 to 2 of the radiator fan switch plug are jumped, but fast speed does not work when pins 2 and 3 are jumped. EDIT: both speeds now work fine in this test. Not sure if it's a gremlin or if i forgot to turn the key on.

When the fans are tested directly by grounding pin 3 and applying direct battery power to pin 1 of the driver side fan connector, the fast speed kicked in. Applying power to pin 2 enabled slow to work. The fast speed worked using the same method for the passenger side, but not the slow! I performed the tests multiple times to make sure I wasn't doing anything wrong and the kept getting the same results.

The reason I am testing the fans is because the A/C does not work. The compressor will not kick in and the fans do not work when the A/C button, albeit lit up, is pressed. I am told that if the fans do not kick in when the A/C button is pressed, it is ideal to diagnose any problems related to the fan circuit first before diagnosing the A/C. I've also checked the fuses above the battery, pulled em, and checked underneath just to make sure they were not bad.


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## Budsdubbin (Jul 14, 2008)

I can say that I have a similar case. Low speed fans work when jumped from 1 to 2, but high speed will not jump. A/C is evacuated, a/c high pressure switch is removed (pigtail open). I believe it may have something to do with it but I cannot for the life of me connect the dots. First day back at VW starts monday so I'll do a bit more research and report back.


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## K C (Jul 26, 2014)

Make sure you have the key on (engine off) when doing the high speed test from the thermoswitch. It will not work if the key is off. I think that's what happened in the first couple of tests, leading to confusion. Now it looks like the FCM is at fault even though I still cannot figure out why the low speed will not work on the passenger side fan when tested directly.


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## Troil (May 9, 2012)

I'm struggling with neither of the fans working. The fuses are okay, although the 30amp fuse in the aux. box had practically melted. Replaced that, and tested it with a lamp along with the 40amp link.

Power is going to the control module connections as well, however there is NO power going to the actual 3-pin plug to the radiator. I tried that with the test lamp as well, and the only reaction was the doors locking and radio turning off for a bit? I assume it's shorting out somewhere. Anyone experienced this particular problem, and possibly a location where to start looking?

Thanks


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## Troil (May 9, 2012)

Troil said:


> I'm struggling with neither of the fans working. The fuses are okay, although the 30amp fuse in the aux. box had practically melted. Replaced that, and tested it with a lamp along with the 40amp link.
> 
> Power is going to the control module connections as well, however there is NO power going to the actual 3-pin plug to the radiator. I tried that with the test lamp as well, and the only reaction was the doors locking and radio turning off for a bit? I assume it's shorting out somewhere. Anyone experienced this particular problem, and possibly a location where to start looking?
> 
> Thanks



I'm now replying to myself in case it helps someone else. I popped open the fan control module, and tried connecting the coils manually. The higher speed side worked fine, but the lower side was not getting any power. I temporarily joined the two together, and both sides worked just fine, AND power was coming to the 3-pin plug at the radiator as well. So a new control module is needed.

Just a word of warning, in case your car is as old as mine, and you're not sure whether it's the control module or something else, use caution while removing it. The plastic had probably been maturing in the engine bay for 16 years, and the bolt holders snap rather easily...


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## krafty-max (Aug 14, 2010)

Does anyone know if the FCM can effect the function of n112 and the sai ? I remember seeing a form saying that the relay that controls n112 is in part connected to the FCM.... I guess because the sai comes on a certain tempature...the thermo fan switch? Does the sai use the thermo switch? ?


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## krafty-max (Aug 14, 2010)

I am having a strange issue with the n112....any input?


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## Devil_Inside (Jun 20, 2006)

I know that this is an old thread, but it contains the most relevant information to the problem that I am experiencing.

I have a 2000 Audi TT 1.8T and recently both my AUX fan and the AC fans stopped working. After doing some research I decided that most likely the problem lies with the notorious fan control module so I ordered an OEM replacement hoping that this would solve my problem. I replaced the fan control module, but unfortunately the problem still persists. This is when I stumbled upon this thread, which helped me perform some additional troubleshooting.

I disconnected the thermo switch and after jumping the low speed and high speed pins I discovered that both fans only run at high speed (jumping pins 2 and 3). When I jump pins 1 and 2 I get nothing. I get the same result using the original fan control module and the new one.

Do you have what could cause both fans to only run at high speed? I do not have a wiring diagram for the car, but from what I can tell both fans have individual connector which plug to something, presumably the fan control module. I know that the fan control module uses pulse modulation to control the speed of the fans, but if the module itself is working correctly, what else could be causing this problem?

I did not have a chance to perform the test procedure for the fan control module itself because the instructions are written for the 14-pin module, where my car uses the older 10-pin version found on 1999 models.

Any help would be greatly appreciated!


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## fsds1234 (Feb 11, 2003)

just to add my confusion to this thread...

A/C and fans work fine when temp is below 90 or so outside. This issue of mine actually started end of last summer but since temps were not above 90 till now AC has been fine.
So AC works fine when temps are below 90, and also when car is moving due to airflow.

At end of last summer I replaced the FCM with no change. Did some testing...

1. Car off, ignition on, AC set to high- fans spin up
2. Car on- fans will kick on when up to temp. Normal behavior.
3. Turning on the AC the fans still run for a few seconds but then turn off, causing the AC pressure to get too high, shutting off the AC.

I can jump term 1-2 on thermo switch and fans spin low speed. Jumping 2-3 on switch and the fans run for about 1-2 seconds and turn off. re-jumping will cause them to again run for a second or so.

Tomorrow I'll see if I can directly jump the fans and also see if I can measure the resistance. One of the fans was replaced last year. Also, the fuse box on top of the battery had melted and was replaced last year.


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## fsds1234 (Feb 11, 2003)

to follow up...I tested the fans and they were fine. So I purchased a second new fan control module and that fixed the problem. Really hate when you are 98% sure, buy a new part, and still have the same problem, only to have it be that the new part you bought was also broken. :banghead:


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## 8up (Mar 1, 2011)

*Im stumped, Please give me a hand*

So I just recently bought a 337 gti. here is basically my problem list: high idle, low rev limiter, just runs like crap, and the cooling fans only turn on when i have the ac on. EVERY one of these problems is fixed except for the cooling fans. I replaced the green coolant temp sensor, and the radiator fan switch. even with these fixes my cooling fans still don't turn on automatically and the car will overheat. Although, when i turn my a/c on, the fans will fun the whole time. Please give me some help with this.


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## groggory (Apr 21, 2003)

fsds1234 said:


> to follow up...I tested the fans and they were fine. So I purchased a second new fan control module and that fixed the problem. Really hate when you are 98% sure, buy a new part, and still have the same problem, only to have it be that the new part you bought was also broken. :banghead:


Most parts come with a warranty. FYI.


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## zoidmk5 (Sep 17, 2006)

I have been having problems for a very long time now with my fans in my 03 GLi 24V. the car runs perfect temp while driving, but if the car sits at idle for a few minutes or more after driving on a relatively warm to hot day, the water temp starts to rise, but goes back to normal after driving again...also, AC works no matter the car temp, never been an issue

so I finally decided to look into this, and after reading several threads and watching videos, I checked the power box above the battery, all of my fuses are good, as is the 3rd wire going to the box...I did the jumper test to test for my fans, and found that neither fans turn on during low speed test, and only the small fan turns on during high speed test

does this indicate that my large fan is dead? also, I know that both fans are suppose to turn on during high speed, but what about low speed?


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## DraganUS (Mar 7, 2015)

Your low speed should turn on when the ignition is off. 
High speed should turn on when ignition is on and you jump start wires on thermo rad switch.

Reading what you said it looks like fan control module is bad and also could be that your big fan is dead as well.


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## zoidmk5 (Sep 17, 2006)

DraganUS said:


> Your low speed should turn on when the ignition is off.
> High speed should turn on when ignition is on and you jump start wires on thermo rad switch.
> 
> Reading what you said it looks like fan control module is bad and also could be that your big fan is dead as well.


I understand that and that is the way I did it...I just want to make sure that based on the fact that nothing came on during low speed test, and only small fan came on during high speed test, that there aren't other tests I can perform and that the large fan is for sure dead

I would still like to know if, under proper working order, both fans come on during low speed operation?


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## dennisgli (May 17, 2003)

zoidmk5 said:


> I would still like to know if, under proper working order, both fans come on during low speed operation?


Yes, if neither fan comes on with power to the low speed circuit then they are both bad.


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## zoidmk5 (Sep 17, 2006)

dennisgli said:


> Yes, if neither fan comes on with power to the low speed circuit then they are both bad.


but the smaller fan, the one for the AC, comes on when I turn on the AC, and when I do the high speed jumper test


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## 8up (Mar 1, 2011)

anybody have a suggestion


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## dennisgli (May 17, 2003)

zoidmk5 said:


> the smaller fan, the one for the AC


Huh - what wiring diagram are you looking at that shows that the smaller fan is for the AC???



zoidmk5 said:


> but the smaller fan, the one for the AC, comes on when I turn on the AC, and when I do the high speed jumper test


If the fan runs when you turn on the AC but doesn't run when you test it by connecting power directly to it then you are testing it wrong.


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## 8up (Mar 1, 2011)

*Someone send me in the right direction*

So I just recently bought a 337. Im having problems with the cooling fans. when the car is running the fans do not turn on by themselves, and the motor overheats. when i turn the a/c on though, the fans kick in and it keeps the motor cool. so basically the fans only run when the a/c is on. i replaced the green coolant sensor and the radiator fan switch. i checked all of the fuses on top of the battery and everything looked good. SOMEONE PLEASE HELP


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## All_Euro (Jul 20, 2008)

8up said:


> So I just recently bought a 337. Im having problems with the cooling fans. when the car is running the fans do not turn on by themselves, and the motor overheats. when i turn the a/c on though, the fans kick in and it keeps the motor cool. so basically the fans only run when the a/c is on. i replaced the green coolant sensor and the radiator fan switch. i checked all of the fuses on top of the battery and everything looked good. SOMEONE PLEASE HELP



Your thermostat might need replacing...


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## draganpokrajac2 (Feb 27, 2015)

8up said:


> So I just recently bought a 337. Im having problems with the cooling fans. when the car is running the fans do not turn on by themselves, and the motor overheats. when i turn the a/c on though, the fans kick in and it keeps the motor cool. so basically the fans only run when the a/c is on. i replaced the green coolant sensor and the radiator fan switch. i checked all of the fuses on top of the battery and everything looked good. SOMEONE PLEASE HELP


fan control module. 

Sent from my G7-L01 using Tapatalk


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## 8up (Mar 1, 2011)

draganpokrajac2 said:


> fan control module.
> 
> Sent from my G7-L01 using Tapatalk


I have tested two different fan control modules in it and that doesn't seem to be the problem.


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## dennisgli (May 17, 2003)

8up said:


> So I just recently bought a 337. Im having problems with the cooling fans. when the car is running the fans do not turn on by themselves, and the motor overheats. when i turn the a/c on though, the fans kick in and it keeps the motor cool. so basically the fans only run when the a/c is on. i replaced the green coolant sensor and the radiator fan switch. i checked all of the fuses on top of the battery and everything looked good. SOMEONE PLEASE HELP


I'd check the thermal switch on the radiator.


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## 8up (Mar 1, 2011)

I already placed that


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## formerly silveratljetta (Feb 6, 2007)

8up said:


> So I just recently bought a 337. Im having problems with the cooling fans. when the car is running the fans do not turn on by themselves, and the motor overheats. when i turn the a/c on though, the fans kick in and it keeps the motor cool. so basically the fans only run when the a/c is on. i replaced the green coolant sensor and the radiator fan switch. i checked all of the fuses on top of the battery and everything looked good. SOMEONE PLEASE HELP


I have same problem and replaced both radiator fan switch and the fan control module but still have the same problem. No solution yet.


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## dennisgli (May 17, 2003)

8up said:


> I already placed that


Why did you replace it? Did you test it and found that it is bad? How did you test it?


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## formerly silveratljetta (Feb 6, 2007)

formerly silveratljetta said:


> I have same problem and replaced both radiator fan switch and the fan control module but still have the same problem. No solution yet.


Have you considered the possibility of a failing water pump not circulating the coolant properly?


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## arto (Jan 3, 2015)

I've had the same problem for the past year also. Everytime I've seen this posted it never gets resolved. 

I've replaced the FCM, thermoswitch, thermostat, and the CTS, but none of this has solved the problem. All my fans and fan speeds are working correctly after testing the thermoswitch the way outlined in the Bentley manual. I've noticed that my fans occasionally don't turn on all together when idling for long periods without the A/C causing the temperature to rise above 105 degrees, but by then I turn on the A/C to cool it down. When they do turn on after idling without A/C, they come on at about 99 degrees and turn off at about 93. From what I've read low speed is supposed to turn on at about 95-96 degrees, and high speed at about 100-102. So I think my high speed is probably fine, but low speed is not working correctly. Also, I've read that low speed operates by only going through the thermoswitch, which I've already replaced. All I can think of doing is replacing that once again, but I don't want to buy another just to have the same problem. Has anyone that's had this problem ever solved it?


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## formerly silveratljetta (Feb 6, 2007)

arto said:


> I've had the same problem for the past year also. Everytime I've seen this posted it never gets resolved.
> 
> I've replaced the FCM, thermoswitch, thermostat, and the CTS, but none of this has solved the problem. All my fans and fan speeds are working correctly after testing the thermoswitch the way outlined in the Bentley manual. I've noticed that my fans occasionally don't turn on all together when idling for long periods without the A/C causing the temperature to rise above 105 degrees, but by then I turn on the A/C to cool it down. When they do turn on after idling without A/C, they come on at about 99 degrees and turn off at about 93. From what I've read low speed is supposed to turn on at about 95-96 degrees, and high speed at about 100-102. So I think my high speed is probably fine, but low speed is not working correctly. Also, I've read that low speed operates by only going through the thermoswitch, which I've already replaced. All I can think of doing is replacing that once again, but I don't want to buy another just to have the same problem. Has anyone that's had this problem ever solved it?


Have you confirmed that your water pump is working properly


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## arto (Jan 3, 2015)

formerly silveratljetta said:


> Have you confirmed that your water pump is working properly


Okay, I've just checked I'm getting good steady flow at idle and heavy flow when giving it throttle. But I did notice a little build up on the expansion tank return hose connection. So I cleaned it a little and will see if that was blocking flow. Any other ideas if that's not the problem?


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## Brake Weight (Jul 27, 2006)

It's too hot to be trouble shooting my FCM at this time. But what I was able to determine before getting drenched with sweat, is that there is 4.65v +/- getting sent to my compressor at all times. That's either when the car is not running (without key in ignition) and the AC not switched on, or when the car is running and the AC is switched on. Fans turn on/off with AC when engine is not running, but on initial engine startup they aren't running. But they do come on as soon as the AC is switched on. I haven't let it come to operating temp but I will later this afternoon when the sun breaks over the trees some.


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## formerly silveratljetta (Feb 6, 2007)

Brake Weight said:


> It's too hot to be trouble shooting my FCM at this time. But what I was able to determine before getting drenched with sweat, is that there is 4.65v +/- getting sent to my compressor at all times. That's either when the car is not running (without key in ignition) and the AC not switched on, or when the car is running and the AC is switched on. Fans turn on/off with AC when engine is not running, but on initial engine startup they aren't running. But they do come on as soon as the AC is switched on. I haven't let it come to operating temp but I will later this afternoon when the sun breaks over the trees some.


keep us posted :thumbup:


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## Brake Weight (Jul 27, 2006)

formerly silveratljetta said:


> keep us posted :thumbup:


I was hoping someone could keep me posted. I'm calling a local German Auto Shop in the morning and see if they'll look at it. My mom has an older New Beetle and I'm going to see what, if any, voltage her compressor is receiving. The constant voltage leads me to believe it's the FCM with a stuck relay or something.


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## formerly silveratljetta (Feb 6, 2007)

Brake Weight said:


> I was hoping someone could keep me posted. I'm calling a local German Auto Shop in the morning and see if they'll look at it. My mom has an older New Beetle and I'm going to see what, if any, voltage her compressor is receiving. The constant voltage leads me to believe it's the FCM with a stuck relay or something.


I had the same problem and swapped FCM with no change in symptoms.


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## Brake Weight (Jul 27, 2006)

Local shop was no help. 

-Hello, how can I help you? 
-I have an '04 Jetta with an AC issue. 
-VW? Uhhh. I'll do Mercedes and BMW ACs. Not VW. 
-Would you trouble shoot it and I'll do the work at my house? 
-That's the hard part I don't do. Thanks. 
-???

Looks like I'll need some cool days either way. Troubleshoot and repair or take it to the the nearest dealership 2 hours away.


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## red982.0 (Jan 31, 2005)

This is a great thread, and I've referred to it often over the past two years as I've continually battled with the cooling and A/C problems on my kids' '02 Jetta 2.0. Over the past two years I've replaced the fans, the FCM, and now the Coolant Temp Sensor (again?).

Up until last week, the A/C was working fine, and then it started being intermittent. Finally threw CEL code (16501 - coolant temp sensor), and I noticed at this point neither fan was running even when A/C and fan select switches were on and the engine was hot.

Replaced the Coolant temp sensor this morning when it was 55 degrees outside, turned the ignition to on and the A/C and fan switches on. Looked under the hood and both fans were running, but then aftger about aminute they stopped.

I drove it to work this morning (30 minutes), and still the fans were not on.

I haven't heard anyone else report this issue of the fans coming on for a bit and then going off.

Any ideas from the expert crowd here?

P.S. Why are are VW electronics so bad?


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## groggory (Apr 21, 2003)

check the fuse box on top of the battery. See if the left most ATO fuse is melted or if any fuses in there are hot.


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## red982.0 (Jan 31, 2005)

groggory said:


> check the fuse box on top of the battery. See if the left most ATO fuse is melted or if any fuses in there are hot.


Already done, fuses are clean and not burnt.


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## franciscomk3 (Feb 27, 2012)

Awesome thread guys!

hoping someone might help me out with my A/C on a gti vr6 mk3

Currently when the car is on and warm and turn on the AC (ac light turns on):
No clutch engaging
No fans

Ive tested:
jumped fans at thermo switch -> both speeds work


A little background.
driving home from a road trip 1000+ miles
100` weather
freeway driving
AC was on and i had to come suddenly to almost a complete stop because of traffic
I felt the car was going to stall while braking
turned off the AC because i thought the compressor was seizing
turned on AC at a rest stop. It cooled, fans worked but i thought i head chatter on the compressor and thought it was going bad so i didnt use it for a long time.
NOW: the fans nor the clutch engage!

Should i replace the thermo switch?
Could the seizing (i think it was seizing, i may be wrong) cause the whole system (fans) to not work?

Thanks in advance!


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## franciscomk3 (Feb 27, 2012)

Bump.
Replaced thermo switch and still no fans or clutch kicking in when the ac button is pressed.


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## Garuf (Oct 10, 2015)

My fans just run full speed constantly even if the keys aren't in the ignition. The only way I can stop them is pulling the 30A battery top fuse. Anyone got any ideas?


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## Galant409VR$ (Sep 23, 2015)

well my fans stopped working the other day and today after work I spent some time trying to figure out whats going on. 
I did all the steps on the first page. I first tested the fans, the drivers fan worked when I put power to it but the passenger fan didnt come on. I checked the thermo switch for power at the red wire and the test light lit up. I then went to test the thermo switch by jumping the wires to test low and high speed. first on low fan speed... nothing, then tried high fan speed.. again nothing. The 30amp fan fuse under hood is good and the fuse in the dash is also good. So whats going on? is it the fan control module at fault? Im getting power to the thermo switch? how do I test the fan control module to confirm that thats the issue?


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## markeysscirocco (Oct 23, 2006)

*Low fan Nothing?*

Ok well, in my case with and older VR6 95' Passat I did all the tests, Thermo switch connector jumping 1-2 and 2-3 and got nothing but the relay in the Fan Control Module closes/clicks and that's it. Same thing at the after run sensor. Changed control module with a spare and got the same results. I get high speed fans only when the temp reaches 230 deg. which is when the emergency fans kick on. all three sensor switches show good. I get 12v at the large red wire on rad fan switch/thermo switch connector. low fan speed may be inop in the fan motor itself (resistors) for low speed. What about high speed? 




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## alekslove (Jan 30, 2016)

*Tested 2&3: good! tested 1&2: nothing! please help*



Andaloons said:


> 1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
> 2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
> 3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
> 4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
> ...


Thanbks for these instruciton, yet, when I tested the 1 and 2 terminals, i got nothing, but did get the high speed on with 3 and 4. You did explain what nexts steps to take if you got the fans to trun on with both sets of terminals, but not with only 2 and 3 turning on. What do you suggest I try next if only 2 and 3 are turning on, but I get nothing with 1 and 2. Thanks!


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## markeysscirocco (Oct 23, 2006)

I ended up just getting another used fan and had no issues since. The resistors for the low speed fan goes bad.


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## KCO (Jun 1, 2012)

Is it possible to replace the fan control module for two simple relays?

My car was badly repaired and does not.


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## Elvir2 (Nov 19, 2007)

Andaloons said:


> 1. To test a fan motor, unplug the electrical connector at the motor and use fused jumper wires to connect battery power and ground directly to the fan. If the fan does not operate, replace the motor.
> 2. If the motor tests OK, check the cooling fan thermo switch, located at the bottom of the radiator on the driver's side.
> 3. Remove the electrical connector from the cooling fan thermo switch and apply a fused jumper wire between terminals number 1 and number 2 with the ignition switch in the ON position, with the engine not running. Both engine cooling fans should run at low speed.
> 4. Next apply the fused jumper wire between terminal number 2 and number 3 with the ignition switch ON and the engine not running. Both engine cooling fans should run at high speed.
> ...




I just did this test.

Checking fans by applying power directly to motor. Primary fan dead as a door nail. Auxilary fan works on both speeds.

Second test i did via thermo switch, and only aux fan ran under low speed, i did the high speed but the aux fan stsrted running for a sec and then i hear a click and it stops. I did this several times with same result, i wonder if this an issue past the fans..


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## Elvir2 (Nov 19, 2007)

Btw, would anybody recommend not buying oem fan. Ecs has different brands meyle and ht i believe for half the price but saw no reviews


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## valet (Apr 21, 2002)

Semi related question:

what causes the fans to run after shutoff? My fans work as they should when driving, idling, and when the AC is on, but DO NOT run when I shut off the car as in after-run. Drove around today for about an hour in stop and go traffic in 100F+ weather with absolutely no cooling fan problems (new FCM, new thermoswitch, new large rad fan - all replaced because my temps would spike over midline in stop and go traffic).

Dropped off some stuff at the dry cleaners and got back into my car and noticed that the temp gauge registered one line over midline. Within a few seconds of driving, gauge moved to middle again. Got home and fans did not run when I switched off the car. Checked all fuses (5, 16, 25, and 40a fuse in the box (and 30a fuse)) and all look good and no melted plastic. In a working after-run situation, do both fans run, or just one, and which fuse/relay controls it?

thanks


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## valet (Apr 21, 2002)

Not sure if I solved the problem but the issue has gone away. My car has been missing the ambient temp sensor (in front of rad) and I was able to pick one up for super cheap. Slapped the sensor in, and after my next drive, after run fans came on when I stopped the car...


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## .:RyouExperienced (Sep 19, 2005)

Hey Guys,

I just wanted to double check that my large fan was dead with everyone. The low and high speeds on the small fan worked great when jumping the thermo-switch but the larger fan did not.

Would it be safe to say that the large fan is dead at this point?

I can't imagine the FCM circuits for both speeds would fail for the large fan simultaneously and all fuses/wiring is good.

:beer::beer::beer:


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## Kumba1 (Feb 19, 2011)

So when I run mine on highspeed everything checks out. When I test the low speed my paperclip gets super hot really quick, but still seems to run the fans fine. Any reason? I think this may be messing up my thermoswitch


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## slavik19 (Feb 9, 2010)

man i hate to grave dig but will this method work on a R32 it has climatronics 

?

Sorry and thank you in advance


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## Fabianayala (Dec 20, 2017)

Hello i have a 2000 MK4 GLX Jetta and 1 day ago A/C stopped working and noticed that with the car on iddle A/C On high or low speed fans don't kick in
not even if the engine reached normal temperatures.

I removed the 3 pin fan switch and jumped Pin 1 and 2 and both fans activated in low speed (ignition off).
***But when jumped pin 2 and 3 (ignition on) high speed fans didn't work***

Also tested the Fan control module T14 pins and T14/ (8, 9, 4) have 12v
***But in pin T14/6 Ground signal is absent***

T4 plug has positive 12v in 1 & 3 
and Ground in 2 & 4

S164 and S180 fuses are ok

Plug T14/ 5 & 14 have continuity

What should i buy or test next ??
Excuse my ignorance i am a DIY beginner


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## johnhorgan1 (Nov 16, 2020)

*No earth at connection to fan control module*

Put a jumper lead from negative battery terminal to engine and see if you have restored the earth at the test point.
If no earth at test point you could run a seperate feed to the connection that is supposed to be earth.
The fans will not work without positive and negative feed.


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