# Radiator cooling fan test on a 2007 New Beetle with a BPS engine



## Tinkergong (Jan 16, 2019)

I have a 2007 New Beetle with the BPS 2.5 liter 5 cylinder engine and I would like to validate the operation of the radiator cooling fan unit. It has a 4 pin oval connector located on the driver side just below the radiator which in the VW manual is called T4. My original intention was to disconnect the 4-pin temperature sending unit and jumper a 220 ohm resistor from pin 3 to 4 to simulate a coolant temperature of just under 200° F. I did that, but it didn't start the fan, so I would now like to stimulate the fan controller myself to see it the fan spins without depending on the motronic controller to do it. 

I measured the voltages at the oval 4-pin connector that leads directly to the fan contoller. Here is what I found.:

Pin 1 (red wire) 12 volts with the ignition key "On" or "Off".	This wire seems to bridge the motronic contoller (J220) to the fan motor controller (V35).
Pin 2 (blue and black wire)	12 volts with the key "On" only and with or without the temperature sender connected. According to my schematic Pin 2 comes from terminal 178. 178 means nothing to me. 
Pin 3 (red and green wire)	0.38 volts d.c. and 0.9 volts a.c. with the key "On" and a 220 ohm resistor across T4/3 and T4/4. I got the same values with the temperature sender connected, but always 0 volts with the key "Off". This wire supposedly goes to Pin 66 on the 121 pin motronic controller.	
Pin 4 (brown and black wire)	0 volts all the time (The ground was good.)	

Somewhere on an Audi site I read that Pin 3 was an "activation wire". Somewhere else I read that the fan speed is regulated by pulse width modulation. Because of that I hooked up an oscilloscope to see what it would say about Pin 3. I got a less than 2 volt pulse train that was on for only about 20% of the time. It makes me suspect that the fan controller is not being triggered because the voltage is too low, however, the pulse duty cycle didn't not seem to change when I lowered or increased the resistance at the temperature sender. 

Anyway, one thing I would really like to do is to test the fan unit so at least _that_ has either been confirmed or eliminated as a failed part.	

I can easily separate the fan controller connector, apply battery voltage to Pins 1 and 4. If some one tells me that it is appropriate, I will also put 12 volts on Pin 2. Pin 3 is a mystery still and I would greatly appreciate it if someone could tell me a quick and dirty way to stimulate it without damaging the fan motor controller, but at the same time verifying the functionality of the controller. 

The car shows no errors other than over-temperature when it starts to overheat because the fan doesn't run. My generic code reader shows no errors at all. 

This problem and a slew of others, began when I went away for a few weeks with the car parked at a very slight incline. I had just bought the car from someone who had kept it garaged for all of its previous life. That is significant because when I came back the car had 4 inches of water in it everywhere. I discovered a design defect which caused the serious leak and corrected it as best I could by drilling a couple of drain holes near the bulkhead and using copious amounts of plumber's putty. Nevertheless the damage to the electrical system was done. 

Which reminds me, can anybody tell me where the J386 and J387 door control units are located?

Finally, I believe what I have described to be accurate, but you never can tell with shop manuals that don't really have the exact wiring schematic. Nor can you be sure with Heffalumps.


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## billymade (Jan 29, 2008)

The fan control module, is integrated into these fan assemblies; unfortunately, that makes the assembly expensive to replace. Here are some service manual links; hopefully, that will be helpful: Note: #5 Coolant Fan Control (FC) Control Module J293

https://workshop-manuals.com/volksw...ntrol_module/component_information/locations/

wiring diagram: 

https://workshop-manuals.com/volksw...agram_information_and_instructions/page_4133/

cooling fan thermal switch location: 

https://workshop-manuals.com/volksw...ensor/switch/component_information/locations/

Most of the time, we have seen the motor or the fan control module fail. The assembly from the dealer is expensive, as you cannot buy the parts separately; you can save some money by going with a oem part. :banghead: Genuine VW, seems to be in the $500+ range and aftermarket $350. A good used one from a junkyard; might be something to look into, even if, you just use it to confirm, the part is good/bad but ultimately, a new oem part, is recommended for a long term reliable cooling solution. 

Brose, seems to be the current genuine VW oem and photos online; shows them, to be made in Germany and other sites, show VDO, which is another typical oem for VW cooling fans. 

Pretty sure, this is the right one: VW part # 1C0959455F
Genuine Engine Cooling Fan Motor; 500W; 370mm Diameter

https://www.google.com/search?source=hp&ei=hsBAXKvXJYOXjwS-2YbQAw&q=1C0959455F&btnK=Google+Search

I don't know if we have helped any; let us know, what your troubleshooting results are and what part you decide to go with. Thanks! :wave:


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## Tinkergong (Jan 16, 2019)

*Billymade, many thanks for your research, but ...*

I still need to verify the operation of the fan. Unfortunately, the thermal switch you linked a photo to for me doesn't really exist on my 2007 BPS engine. The link to the exploded view of the radiator seems to be more accurate. The fact that there is no simple thermal switch that I could just jumper to activate the fan is what has me stumped. The wiring diagram you sent, was appreciated, but it doesn't really tell me what I need to know about what the signals should be. 

I need to turn on the fan right at the 4-pin connector on the radiator (listed as #15 on the diagram you linked to.) before I go out and try to buy a new one, or even a used one for that matter. There are still a number of other parts that could be bad instead, or in addition.

I do indeed appreciate your information on purchasing a fan with controller unit. It may come in handy soon. 

Thanks so much for your help.

P.S. To try to be clearer, there must be a pair of low-current signals (based on the wire gauges) at pins 2 and 3 of the 4-pin oval connector that can be input to activate the fan. If I knew the characteristics of those signals, I could run the fan and thereby verify whether it works or not. There may be an easier/better way to do that which I would be pleased as punch to know about, but I know that the turn-on voltages of pins 2 and 3 will suffice. 

Also, by the way, all of the Youtube videos I have been able to locate thus far have been based on an older style and electrically simpler 3-pin connector located in about the same place that is for the two-fan systems.


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## tafossa (May 5, 2019)

*same problem*

Tinkergong,

did you ever find out what your problem was? I have the same radiator fan issue and Beetle model. But my fan runs full blast all the time. I can't seem to figure out how to trouble shoot it?


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## Tinkergong (Jan 16, 2019)

*Radiator fan with a single fan troubleshooting (2007 New Beetle)*

Dear tafossa,

Before I start telling you what I did, I must say that I have to move and I will not find my notes on my own experience for a good while, so please forgive me for some of the lack of explicit detail except for a few things that I actually typed into my computer. Much of what follows is from memory my only, but since I really had to put a lot into finding out this stuff, you will see that I remember quite a bit.

The order I used in doing things was not necessarily the most efficient because I wasn't going in order the most likely problems, but in order of the access points that required the least disassembly first.

On my 2007 New Beetle with a BPS 5 cylinder, 2.5 liter engine there is a 4 pin connector just to the right of the engine coming out of a ~ 20 mm inside diameter coolant hose which is the temperature sensing unit. You can just see it with out taking anything off, but you will need to pull of the plastic heat shield on the engine to get at it. 

From a schematic I bought on-line which was supposed to be what dealer mechanics get to to see pins 1 and 2 are connected through a temperature sensistive resistive element. Pins 3 and 4 are connected through a separate resistive element that varies with the temperature. (Read the paragraph below that begins "Armed with this" for more specific detail about which wire is which.)

Coolant temperature sensor:
pin 1 is purple and goes to T121/93 (Where T121 refers to a connector number that VW uses.)
pin 2 is brown with a white stripe and goes to D103 (engine wiring harness at position 2)
pin 3 is blue with a grey stripe and goes to #255 (instrument panel)	
pin 4 is brown with a red stripe and goes to #234 (instrument panel)	

From some automotive help site (probably this one, but I can't remember) I found this (which was for the closest match I could find, and I assumed perhaps naively, that Bosch, or whichever manufacturer makes the temperature senders, has very few electrical changes in its products.):

Coolant temperature sensor

Temperature Ohms
68°F (20°C) 2200-2700
158°F (70°C) 400-480
194°F (90°C) 210-280

"Somewhere in the low (0-150) and high (2000+) the car will default to limp mode due to the setting being out of range.
If you hit the limp mode, timing locks in to set timing"

Armed with this, I thought that if I were to jumper pins 3 (blue/gray stripe) and 4 (red/blue stripe), I could get my radiator fan to turn on. In your case you would want to jumper a resistance of more than 500 ohms to pins 3 and 4, Since the resistance of the element in the sensor goes down as the coolant temperature rises you can use this to see if your engine control computer is behaving itself. At more than 500 ohms, your fan should be off. Pins 1 (purple) and 2 (white/brown stripe) go to the instrument panel on the dashboard, so you probably don't have to do anything with them. Just leave them unconnected. I did. If you can't the fan to turn off, at this point, read on. If it did go off, buy another temperature sender. Evdently you just slide out the keeper clip and then pull out the sending unit. There is a Youtube video with someone doing that.

The next thing I did was to disconnect the 4-pin oval connector that is at the bottom of the radiator that goes to the fan motor controller which is integral with the fan motor. I got some male spade connectors and made jumpers to connect all 4 wires so that I could put a probe on my newly created test points. the 12 volt power (pin 1, red ) and the ground wire (pin 4, brown and black) as if I had not removed the connector. Since I was unsure of which of pins 2 and 3 were the ones I wanted to look at, I just decided to measure the voltages at every connector pin. Then I borrowed an oscilloscope and looked at the voltages while I changed the resistances that I was substituting for the coolant sensor. There is a pulse train that is full on for a short period of time, and then off for a short period (the duty cycle). When the radiator coolant is under about 165 degrees F., the duty cycle should be zero. In other words the voltage at either pin 2 or 3 (Sorry, I don't remember.) should be zero all of the time. I am aslo sorry, but I have forgotten how long a the duty cycle lasted, but it wasn't hard to find when I changed the time scale on the oscilloscope. The pin-out was as follows:

radiator fan controller connector

Looking at the female pin side (coming out of the harness from the engine) Pin 1 is on the far left. Pin 3 is at the top if you consider the little raised plastic portion on the oval connector to be at the top. Pin 2 is directly below Pin 3 and Pin 4 is at the far right. 

pin 1 is red	which comes directly from the battery	- # 8
pin 2 is blue and black which goes to #178 (Wherever that is. I have seen it referred to as "switched control".)
pin 3 is green and red	which goes to the T121/66	(I have seen this referred to as "activation wire".)
pin 4 is brown and black	which goes to ground	

In your case, you probably you will probably be seeing a 100% duty cycle. If you cannot get it to drop down by disconnecting pins 3 and 4 at the temperature sensor connector above on the left side of the engine (as if you had connected a resistor with almost infinite resistance) , your drive computer has a problem, or there is a short circuit that is letting the computer measure more current than it should based on the temperature. Finding such a short may require a lot of disassembly of interior paneling. That was what cost me the most time and grief. 

There is one more circuit that might be the culprit and that is the ambient air temperature sensor that is supposed to turn off the fan when you are driving so fast that having the fan on is pointless. That is not so likely in your case because it would involve having the ambient air temperature be measured as higher than it actually is, and the coolant temperature sender measuring the coolant temperature as hotter than it actually is so that the difference stays small so the fan thinks it has to be on all of the time. It certainly is possible though to have two sensors simultaneously go out of specification. (The ambient temperature switch on the VW schematic is listed as connecting to the "Motronic control unit" (J220) at connector T121 pin 50 and has a blue/yellow striped wire which goes to the sensor and then leaves by a blue/black striped wire that goes to T121 pin 31 at J220 as well). 

The vehicle speed sensor could also read as if you were travelling much slower than you are, but I would expect other engine performance problems to go along with that, so think about that last. 

I can't say I have any experience with the ambient air temp sensor, but this is what I found on the Internet:

Intake air temperature sensor: 
30 °C should be resistance of 1.5 to 2.0 kffOhm
80 °C should be resistance of 275 to 375 Ohm 

Good luck with your car! I would be curious as to what you learn. 








tafossa said:


> Tinkergong,
> 
> did you ever find out what your problem was? I have the same radiator fan issue and Beetle model. But my fan runs full blast all the time. I can't seem to figure out how to trouble shoot it?


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## tafossa (May 5, 2019)

Tinkergong,
Thank you for all this info. I appreciate it. For $10 I replaced the coolant temperature sensor, which unfortunately didn't change any thing. The fan's still blasting. I suspect that the problem is with the fan control module. But it's a $500 part, so I'm treading lightly before commiting to replace it. I will take your suggestion to unplug the sensor to see if the fan will turn off. Failing this, I think I will take it to my local VW repair shop to confirm the fan module failure before spending the big bucks. I am considering just buying a used replacement if I can find one reasonably priced. Thanks again,


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## tafossa (May 5, 2019)

*Repair shop confirmation*

Hi, the local VW repair shop confirmed that the control module needs to be replaced. Thanks for your help.


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## tafossa (May 5, 2019)

*the beat goes on*

Tinkergong,

Well I replaced the radiator fan per the troubleshooting guidelines of my local VW repair shop. Pretty proud of myself for being able to pull off the front end. Unfortunately it didn't fix the problem. The repair shop took mercy on me and spent alot of time trying to determine the problem after I had done all this replacement work and ate the cost. They finally said they thought it was the ECU, but didn't have the dealer programs to fully confirm. So now its at the dealer. The plot thickens. The dealer called yesterday and stated that they ran through their hourly troubleshooting time, confirmed it wasn't the ECU, and asked for more troubleshooting time to fully check the wiring. Do you recall specifically where under the dash did you have your wiring short? Perhaps I can give this info to the dealer to check out. Thanks for your help, Tim


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## tafossa (May 5, 2019)

*summation*

Well the dealer finally determined that the problem was a broken wire in the wiring harness. This fixed the issue, or so it seemed. Well a month and a half later, the overheating idiot light came on when I turned the A/C on. Discovered that the radiator fan wasn't running when the A/C was turned on, which it should. Thankfully I had kept the old radiator fan. The dealer plugged it in and determined that the control module on the DEPO replacement fan which I had installed was defective. So I pulled the whole front end off, again. Put the old OEM fan back in. Sent the aftermarket fan back for refund. Now everything's working again.


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