Is this the heater clip problem? Seems like something else
 

85.5 944 NA

I usually leave my dial on coldest setting and with re-circulation off. I get air from the outside. Dandy. When I use heat (I've had to use the defrost, which puts on full heat), I keep heat even after I turn the defrost off, or put the dial back to cold (I've only done this using the defrost button). It's terrible. Full heat coming in.

If I play with the dial enough it seems, it will get back to 'cold'. I do full sweeps, slowly, then quickly, just play with it until finally when I am about to give up (a few minutes, while driving), it goes to full cold.


I don't think my heater clips are broken, because it 'eventually' comes back/goes where it should. I have no clips (2pc of the two different things). Maybe it's just dirty? What could I shoot that with? WD 40? Pb blaster? I think there were pics on Clarks garage.

The clips are for the "doors" by your feet on the driver side. From what you describe, with a late 85, it sounds like the temp control module is going bad. Late cars are electronic, so there are no cables that can get stuck....so nothing to wd40 or pb.

From Clarks Garage, but mine seems different. Cracked Vacuum line?
"Full Heat at All Temperature Settings (1985.5 and Newer 944s)

On late model 944s (1985.5 and newer), there are several problems that can cause the full heat condition. The first and most common problem is a damper linkage in the driver's side footwell (for left-hand drive cars). Stick your head in the footwell and look up and toward the center console. You should see a small diameter metal rod which rests in a white plastic support and is held in place by a metal retaining clip. On later model 944s, there are two damper linkages instead of one and they are located behind a plastic cover. One of the plastic clips on the linkage may be broken preventing the linkage from operating the damper. When the damper fails to operate, the system fails to full heat. Most German cars are designed to fail this way. It's a safety feature to keep you from freezing in winter. The first picture below shows a linkage that has come loose from the support because the metal clip is broken. The second picture show the linkage properly in place with a new support and clip along with the part numbers for the support and clip.





The second problem is with the heater control valve. The heater control valve is vacuum operated and located at the back of engine near the firewall. There is a vacuum line which goes from the valve to a vacuum connection at the firewall where the heater hose connections penetrate the firewall. Check this vacuum line to make sure it is connected and doesn't show any signs of cracking. There is another vacuum line fitting near the heater hose connections which goes to a rubber "Y" connector. One side of the "Y" goes to a small check valve attached to the large brake booster vacuum line at the back of the firewall. The other side of the "Y" goes through the firewall to a plastic vacuum retention canister next to the battery. Make sure all these lines are connected and don't show any signs of cracking. If all vacuum lines are properly connected you may wish to remove the heater control valve from the system and check it's operation with a vacuum tester. A problem with the heater control valve opening may also be caused by the vacuum solenoid valve going bad. Remove the solenoid and apply 12 VDC to valve to see if it opens and closes properly. If you look at the picture titled HVAC UNIT RIGHT SIDE above, the solenoid is component #3.

Finally, a full heat condition can be caused by a failure of the Temperature Control Unit (TCU) itself. Unfortunately, I don't have a good way to test the TCU at the moment. And, they're quite expensive unless you can find one from a car that's being parted out. So, replace the TCU as a last resort. "

ja.