2004 2.0fsi fan doesn't turn off

[Smithy361]

I've just bought a 2004 A3 and was driving fine all day today. Pulled up tonight as it started raining and the radiator fan would not turn off at all. Had to pull the battery lead for it to stop running at full speed. The fan was still running full speed 10 minutes after turning the car off.

Any ideas what I should be looking at to fix this?
Thanks

 

[aqibi2000]

unplug fan connectors, clean and plug back in then measure the fan control signal to see if the duty cycle changes (signal from PCM).

This can be triggered via VCDS to output test the fan.

if signal is correctly measured then the fan has a built in pwm driver which could be faulty - swap fan for second hand parts.

 

[Smithy361]

unplug fan connectors, clean and plug back in then measure the fan control signal to see if the duty cycle changes (signal from PCM).

This can be triggered via VCDS to output test the fan.

if signal is correctly measured then the fan has a built in pwm driver which could be faulty - swap fan for second hand parts.

Where do you measure the control signal on the pcm?
Thanks for the reply

 

[prt57]

I had this on my S3 8P after unplugging the connector to the temperature sensor located in the plastic pipe located above the gearbox. After plugging the wiring back in to the temp sensor the fans were turning at full speed when the ignition was turned on, even with the engine stone cold.
So it must have been a dodgy connection in the sensor as a replacement sorted it out straight away.