I just purchased this 94 Cabrio 2.8 engine,134k miles.(Is this a Audi 90?).The cooling fans never come on.I checked the fuses for the fans and all were ok.
Is there a sensor that activates the cooling fan and where is it located?Could it be the water pump?Your input will be appreciated.

 

Turn on the air conditioning and see if the fans come on. Both should operate. That will test the fans themselves. There are several relays and a temp switch involved in this. The temp switch is at the lower right bottom of the radiator. It has a rubber boot covering the connector. Remove the connector and use a jumper wire to jump from the center to the left and right contact position. The fans should operate. If so, you have a bad temp switch in the radiator. If not, you have a problem in the relays. They are located in the auxillary relay panel under the left dash panel, driver side. Of course, there could be a wiring problem, or corrosion under the contacts on the resistor panel, lower left front, tucked up under the fender. This is a start for you.