Audi Repair: 2002 AUDI A4, coolant temperature switch, engine coolant temperature

Question
Both fans turn on when the car is not being used and it is draining the battery.  I was told to replace the battery. Done that it did not work. then I was told it was the ecu.  The only way to keep the battery from draining is to disconnect the negative cable.  I have seen some postings on this but no actual fixes.  This is my sons car and I hate to keep spending large $$$ on a cheap fix.  Thanks

Answer
The engine coolant temperature switch located in the radiator is probably the culprit.  This is a cheap fix, once you get to the part.  You will need the new switch, and coolant.  First try to disconnect the swithc and see if the fan stops.  The switch is usually in the lower section of the radiator.  Let me know,  Jan