2001 A6. Neither of the electric fans (condenser or radiator) come on with or without the AC being switched on. The only fan keeping the engine cool is the viscous fan. I noticed this problem when stopping at a stop light, the AC starting to get warm. I don't know where to find the relays or fan control unit on this car, but think that is where I think I should look first. Both fans were replaced about 1.5 years ago, so I don;t think they are the problem. Any ideas out there?

 

Since they run with the AC on, the fans are OK. They are controlled by the PCM Fan Control Module, it's on the Driver's side up front (follow the wires from the fans). There are 3 fan speeds, 50%, 85% and 100%. If you only get fan when the AC is on, then either the FCM isn't getting the turn-on signal from the thermostatic switch F18/F54 or there's a problem with the FCM itself (doubtful, since the FCM turns the fans on with the AC).
There are two fuses for the FCM; they're on the under-dash 8-relay panel, sockets 61 and 30 (3rd and 4th from the left side). If they're both good, I'd suspect the F18/F54 ThermoSwitch
Jim

 

Thanks Jim, but neither fan turns on with or without the AC being on.

 

Sorry - I mis-read your first line -
Check those fuses first. If they are OK, then it's most likely the fan control module.
You can test the fans by putting 12V directly on them to see if they run.
Jim

 

Thanks Jim - I will look as soon as I get home!
Scott