My 98 A6 quattro 2.8 is having a problem now with the air conditioner, it sound like the fan might get loose everyonce in a while and it sounds like the fan is clunking really fast, then I turn it of and turn it on and its fine untill i turn or something it is becoming more frequent. Any suggestions

 

the blower motor (inside the car) right? search the forum and you will find the procedure for removal. It's real easy. I would remove it abd inspect it. The squirrel cage may be caked w/ debris?