I have a 1991 100 (non-quatro)
I am replacing the heater core this weekend. When I bought the car, the heater core had been by-passed and I have no idea how the plumbing for it is supposed to be. If any one can help me with a drawing or something, that would be appreciated.
(I dont have the cash to pick up a service manual set just yet)

 

Well I got the heater core in. I am sure it is plumbed up right. the problem now is, no matter what setting I have the heater on, I am still not getting hot air out. I felt each of teh lines that go to the heater core and they both feel hot. I am posistve I got everything hooked up correctly. Any ideas? ( I know its not a lot to go on) but any help would be appreciated

 

thermostat
blower motor

 

Thank you for a response.
The blower motor is working, I feel air movement. I can cycle the doors inside the unit.
On saturday for 1 driving session I got heat out of it. A lot of heat. unfortunately it was during the warmest part of the day and we really didn't need the heat on.
Since that one time though still no heat. I am curious if there is another flap that isnt opening or something.

 

I have exacly same problem with my car and I spend a lot of time trying to figure out what it is but still can't. I have a digital climate control in my 1993 audi 90 cs and I am assuming it might be something wrong with it. Thermostat works, it opens and closes, so I am assuming it is not a problem...

 

How air conditioning works



The temperature in the passenger compartment depends on the amount of heat radiated into the vehicle through the windows and conducted by the metal parts of the body. In hot weather it is possible to achieve a more comfortable temperature for the passengers by pumping off some of the heat.



As heat spreads into cooler areas, the passenger compartment is fitted with a unit for generating low temperatures in which refrigerant is constantly evaporated. The heat required for this is extracted from the air flowing through the evaporator.



After absorbing heat, the refrigerant is pumped off by the compressor. The action of the compressor increases the heat content and temperature of the refrigerant. Its temperature is then substantially higher than that of the surrounding air.



The hot refrigerant flows with its heat content to the condenser, where the refrigerant dissipates its heat to the surrounding air via the condenser due to the temperature gradient between the refrigerant and the surrounding air.



The refrigerant thus acts as a heat transfer medium. As it is to be re-used, the refrigerant is returned to the evaporator.



For this reason all air conditioning systems are based on the refrigerant circulation principle. There are however differences as regards the units used.

that's just a bit of info because its digital setup so it could be the evaporator or it hasn't been bled of air properly ( heat has to be turned up to expel the air from the matrix ) other wise you end up with air in the system when you turn the heat on

 

Rev high.