I've got a 98 1.8T quattro which has an intermittent fault in the AC fan. It will from time to time run and then die then start running again. the motor itself works fine (I think) I've been told that it could be the relay/clutch control
This part here, http://www.autohausaz.com/search/pro...968@AC%20Relay
is supposed to be the one. My local Audi dealer wants to replace the entire AC motor (surprise!!!)

 

Could this cause both your ac and heat to go out?