# Cooling Fans Running Constantly



## gganske (Dec 13, 2009)

Two days ago I had to drive through a few snow drifts on a country road and when I got out of the car with the engine running I could hear the fans running. I popped the hood to make sure there was no snow packed in the engine or lower chassis, then checked under the car and all looked clear. I park in a heated garage at night so the car dries off nicely by morning. Now they are on all the time which is unusual because the outside temp is -20C the past few days. Any suggestions?


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## Prince Ludwig (Mar 24, 2007)

Are you still getting a reading from the outside air temperature sensor? When it's disconnected the fans will run constantly as a safety measure.
Harry


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## gganske (Dec 13, 2009)

If you mean the outside air temp reading I see on my instrument panel then yes it is reading correctly.


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## PanEuropean (Nov 3, 2001)

*Re: Cooling Fans Running Constantly (gganske)*

Greg:
Have a look under the front of the car, slightly towards the left (driver) side, and inspect the physical condition and security of attachment of the outside air temperature sensor.
If this sensor is damaged, or if the connection is loose, or if the wiring harness for the sensor has water in it (that has not yet dried out), then it is possible that the sensor is not working properly and this is why the fans are running.
The car may now be obtaining the OAT displayed in the instrument cluster from a different sensor - that being the one in the left cabin air intake plenum.
Michael
Here is where to find the primary OAT sensor:


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## gganske (Dec 13, 2009)

*Re: Cooling Fans Running Constantly (PanEuropean)*

Thanks Michael I will disconnect it overnight and let it dry out, the photo helped a great deal.
Greg


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## n968412L (Apr 23, 2009)

*Re: Cooling Fans Running Constantly (gganske)*

Be interested to know if this cures it... and does anyone know if this would show up as an error somewhere on a VAG-Com- I imagine it should?
Regards
Mike


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## invisiblewave (Sep 22, 2008)

*Re: Cooling Fans Running Constantly (n968412L)*

It might be difficult for the controller to distinguish between an erroneous and a merely very low reading from the sensor, so if it's getting a signal, albeit the wrong one, it may well not generate a code.


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## PanEuropean (Nov 3, 2001)

*Re: Cooling Fans Running Constantly (invisiblewave)*


_Quote, originally posted by *invisiblewave* »_It might be difficult for the controller to distinguish between an erroneous and a merely very low reading from the sensor....

No, in the case of these OAT sensors, the logic is constructed such that it can distinguish between an out of range signal and an invalid signal.
The actual operating range of the sensor is more than adequate to cope with any free air temperature that could be experienced on this planet - from -40°C to +140°C. The signal can be observed in the measured value blocks for various controllers. If it is invalid, or disconnected, the MVB will report invalid or disconnected.
Michael


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## gganske (Dec 13, 2009)

*Re: Cooling Fans Running Constantly (PanEuropean)*

I unplugged the OAT sensor overnight and even set the sensor over the heating duct for the night to help dry it out. When I unplugged it there was no visible moisture or corrosion inside the connector and the sensor did not look damaged in any way. I am not sure why this sensor would have anything to do with cooling fan operation, would the fans not be controlled by a coolant temperature switch somewhere in the cooling system? My mechanic also did not think it would be the OAT sensor causing the problem. He thinks it may be the fan control modules located adjacent to the cooling fans but I am not wanting to order them because I was told they are $900 CAN each. I could change the OAT sensor easily enough to see if it is indeed faulty, it doesn't look expensive.


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## PanEuropean (Nov 3, 2001)

*Re: Cooling Fans Running Constantly (gganske)*

Greg:
Harry's original mention of the OAT sensor as a possible cause of the problem was (likely) made because you mentioned you were driving through deep snow. If the OAT sensor input is invalid, the radiator fans run all the time as a precaution against overheating - simply because the car cannot determine what the OAT is (it doesn't know if you are freezing your butt off in Alberta, or roasting in Death Valley).
What you now need to do is carry out a diagnostic scan with a diagnostic scan tool such as a VAG-COM or a VAS 5051 or 5052. You can then observe what fault codes have been reported, and this information will then point you in the right direction to repair your problem.
I doubt that both fan control units have failed. But, without a diagnostic scan to look at, it is not possible to speculate further.
Michael


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## turbomeyers (Dec 15, 2005)

I am the tech working on this problem , i scanned it yesterday to find no issues , i will swap out the oat with the one on my s4 to see if it radicates the issue , . i will keep you informed , also these cars have a thermal switch on the radiators , like the old rabbits and golfs that turns on the fans as well . its cheaop enugh to just change as well if the oat thing is innifective ,


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## invisiblewave (Sep 22, 2008)

*Re: Cooling Fans Running Constantly (PanEuropean)*


_Quote, originally posted by *PanEuropean* »_
No, in the case of these OAT sensors, the logic is constructed such that it can distinguish between an out of range signal and an invalid signal.
Michael

And if the erroneous signal is within the operating range? My point was that the sensor might have a fault such that it sends a continuously low or high reading to the controller, especially if the operating range is -40 to +140, which, presumably, the controller would not be able to distinguish from a correct signal.


_Modified by invisiblewave at 9:22 AM 1-8-2010_


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## PanEuropean (Nov 3, 2001)

*Re: Cooling Fans Running Constantly (invisiblewave)*


_Quote, originally posted by *invisiblewave* »_And if the erroneous signal is within the operating range? 

Then it would be obvious to the driver, who would see an unrealistic outside air temperature displayed at the bottom of the small display in the instrument panel.
Michael


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## turbomeyers (Dec 15, 2005)

yea it was not the oat , i ried a test one on it no go . so and the sensor i orderd for iy from vw is incorect so i am looking for the part numbe or the two pin sensor at the pas side botom of the rad ,


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## PanEuropean (Nov 3, 2001)

*Re: (turbomeyers)*

Just phone your local VW dealer, supply them with your VIN, and make sure that you specify that the sensor you want is the one that fits on the bottom of the grille (lower air intake) on the very front of the car.
There are numerous different air temperature sensors on Phaetons, hence the need to specify exactly which sensor you want.
You could also take a very close look at your existing sensor (using a magnifying glass and a strong light), and you will probably find a 9 digit part number in raised relief on the side of it.
Michael


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## gganske (Dec 13, 2009)

*Re: (PanEuropean)*









This is a photo of my temp switch located in the lower rad hose on the car, it looks like a two wire connector. The part number VW gave me is 1J0959481A but the part has a three pin connector and looks too large. Does anyone know the correct part number?


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## KCPhaetonTech (Aug 17, 2008)

*Re: (gganske)*

Hi Greg, 
The ECT part number should be 06A 919 501 A with a seal N 903 168 02.


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## gganske (Dec 13, 2009)

*Re: (KCPhaetonTech)*

Thanks very much, those were the correct part numbers and the fans are working well again.


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## Bindaham (Apr 4, 2014)

Recently, I noticed that my radiator fan is constantly on. Scanned but didn't get any fault related to the sensors.


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## Bindaham (Apr 4, 2014)

Happy to report that the fan came back to normal operation after changing the lower passenger side coolant temperature sensor


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## Bindaham (Apr 4, 2014)

Update:

Fan is still functioning normally, yet that small coolant leak that was there before I changed the sensor is still going on.

Here is a pic after I parked the car for about half an hour. The leak is not constant, it stops after a while.





And here is a shot from underneath which shows the location of the leak. Will check this afternoon or tomorrow wither the hose or the clamp are the problem.


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## Bindaham (Apr 4, 2014)

Update to the update:

A regular hose clamp did the trick. Leak stopped.


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## apper01 (Aug 14, 2010)

any change of exchanging this sensor without taking off the whole front?

blowers are also running constantly, first time it switched off after a while but now they just keep on running.
scanned but no errors came up, so sensor seems to give out some signal volt level but not high enough to generate an error?


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## Bindaham (Apr 4, 2014)

apper01 said:


> any change of exchanging this sensor without taking off the whole front?


Hi there,

The one that I changed is easily accessible from the bottom engine as the pic below shows. 



Bindaham said:


>


Regards,

Salah


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## apper01 (Aug 14, 2010)

so from the bottom, did you take off all the coolant hoses?


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## Bindaham (Apr 4, 2014)

Just the lower passenger side one


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## apper01 (Aug 14, 2010)

Changed the sensor, was indeed not a big job.

Unfortunately the blowers still run on full speed.....

Checked the cables connected to the sensor, seemed ok. And no errors from scanning.

Anyone having a clue were to look next?

PS. is there something like a radiator fan control module on the phaeton or are the blowers themselves equipped with it?


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## apper01 (Aug 14, 2010)

Checked the service manual and there seems to be two temp sensors: G83 (which is on the radiator exit) and G62.

Now i need to find out where G62 is sitting....

found it: http://forums.vwvortex.com/showthre...ngine)-and-improve-fuel-economy-(gas-mileage)

well lucky me: on the V10 TDI AJS G83 is located upfront where the waterpump is, so now need to get another new one and see what happens


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## Dangerrous (Sep 14, 2014)

Have you checked the temperature readings via vcds, When I removed the engine, the sensor on the bumper wasn't connected and the fans were running constantly, even when I connected it back up the fans still carried on running, I had to reset the error in vcds, then I got my temperature reading back. The computer takes an average reading from the two sensors for the climate control and engine control.
D


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## apper01 (Aug 14, 2010)

did not check the water temp with vcds as there were no errors, but will do so tomorrow when i put in the old cleaned up sensor again and will clear the dtc's

took out the temp sensor cleaned it up and checked it's resistance: runs from 0.38kOhms when around 100C to 9.2kOhms when very cold -15C so seems to work

will do the same when i get a new one on friday


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## Dangerrous (Sep 14, 2014)

Sorry, I mean the ambient temperature sensors. The fans also run to keep the ac condenser cool. It may be nothing to do with the engine temperature sensor. Check the temperature readings of the two sensors in the auto HVAC module 8. They are the ones located in a) the front bumper and b) under the scuttle panel next to the engine ecu by the wiper motor.
D


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## apper01 (Aug 14, 2010)

Was looking at the the temp reading for G62 and G83, the readings do not seem to be direclty identified as coming from one of the two.

will sure check the airco temp readings tomorrow, but still will have to exchange G62 as the fan also keeps running if the airco is completely off.
also tried the "reset" option from the media console but that also did not help.


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## apper01 (Aug 14, 2010)

exchanged G62, still the same problem and no errors in VCDS. As i do not have a garage to work in anymore i'll have to bring the car to VW...
this is gonna get expensive


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## apper01 (Aug 14, 2010)

So Garage called back, they have done the standard service and could not find the cause why the blowers are running at full speed so i should take the car home and come back some time later (??)
when they have time too fix the rust and then can have another look at the blowers....

Qoute : "Yes, the car makes some noise but nothing too worry about...." 

There's VW service for you.


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## jimay (Aug 1, 2006)

My fans ran continuously when the thermostat failed (it fails in the open position)

Later on they ran continuously when the thermostat the dealer installed failed (they covered the replacement)


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## apper01 (Aug 14, 2010)

Thanks for the Tip!!

Spoke to the Garage this morning and as they have not yet found the cause told them (?) to check to thermostat and heating element.

Let's see what they come up with....opcorn:opcorn:opcorn:


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## apper01 (Aug 14, 2010)

OK, first garage gave up and now they will sent my car to some special shop nearby which is specialised in the 
electronics of the phaeton (i hope....)


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