91pearl100

I just recently picked up a 1991 Audi 100 with 106k and had a few questions. When the car is running it sounds like the fan is running and air is coming out of the defrost vents. What could this be? Also what can I do to increase performance and fuel mileage? Also, how can I hook my aftermarket radio to run my back speakers as well as the front?

Rusty Spokes

A German thing so you can drive and see out the windshield if the system fails..so you have some kind of fault with your HVAC. Hard to suggest repairs over the internet without more information.

A good service with spark plugs, cap and rotor, fuel and air filters, vacuum lines and all fuel lines checked is a good place to start for a new older Audi.

Check Crutchfield: Car Stereo, Speakers, Home Theater, Pro Audio, LED TV for an adapter harness for your replacement radio.

marcogyver

Is it auto climate control or manual? I am assuming manual. The auto climate can enter a diagnostic mode to check if servos are not moving.

100A8

The rear speakers in the c4 100 is hard. They have built in amps and you have to bypass the amps to put in new speakers in the back