Cooling Fan Module? - Page 2 - VW TDI forum and Audi TDI forum

Ol'Rattler · #11 07-10-2012, 01:48 PM

CD Bentleys shows the temp sensor as a switch and the 2 wires on it go to the ECU. One yellow one Brown. Probably the safest for the ECU would be to unplug the connector and check continuity between the 2 pins on the sensor. The diagram shows the "off position" of the sensor as contacts open so I would assume that continuity through the sensor with the car cold would indicate a bad sensor.

The temp sensor for the fans is located on the lower cooling hose near the radiator, not on the radiator like the text in Bentley's says.

There are two red wires on the controller, the big red wire goes directly to fuse SA 3 (50 amp) and is always hot. The the small red wire goes to fuse SB 24 (10 amp) and then to the B+ Terminal 30 power supply relay. The green wire on the fan controller goes to the ECU and the big brown wires on the controller goes to ground.

14racing · #12 07-10-2012, 08:34 PM

I tried unplugging the temp sensor and the fans continue to run. The controller must be stuck. I assume I need to replace the large fan then? I did run a scan on all of the modules with my vag-com and I did not have any faults. I'm still kind of learning how to use it though. It's much different then what I am used to.

Ol'Rattler · #13 07-12-2012, 05:07 AM

So take it one step farther and T/S the sensor to better understand the system and to rule out the sensor. It could be that sensor contacts open = fan on and sensor contacts closed = fan off. IDK.

If you check for continuity between the 2 pins in the sensor when the car is cold and you get no continuity, then that could support the fact that with the contacts in the sensor are open then the fan should be turned off. You could buy a new sensor (relatively cheap) and run continuity on it to verify that the sensor contact are open when the sensor is cold.

It might not hurt to post in the VCDS forum for specific advise on how to check the cooling fan system. My suspicion is that your controller is bad, but I am not sure how to prove it so that you can verify the controller is actually the problem.