Fan run on
I have a 2001, A4, 2.8L.
The aux. cooling fan runs on until the battery goes dead. In the old days this meant the "Coolant Fan Control" thermal switch (-F18-) was bad, or a bad relay for that circuit.
Reading my service manual I see that there is also a "Engine Coolant Temp" sensor (-G62-).
The manual gives me instructions for testing the circuit but no ohm test for the switches.
I don't want to be a parts swapper. Any advice on trouble shooting would be great.
Re: Fan run on
Found the ohm. test for the ECT sensor(-G62-) and circuit. sensor tests good. On the circuit side pin 3 and 4 show low grade continuity to ground. I don't think this is correct.
Unable to test the "Coolant Fan Control" thermal switch (-F18-) until I am ready to drain coolant, too tight. (Need to find a connector and lead off an old harness) Circuit test for fan speed is not possible because fan is running on high indefinatly. Note that the fan runs on high even if -F18- is unplugged.
The "After Run Coolant Control Module" may also be the devil in the works. The only test listed is that the fan and after run pump must shut down after 3 minutes. Obviously it fails this test by proxy as it pertains to the fan. This may have been the best starting point.