I was having a problem w/ the vent setting in my '88 TA -- when it was warm out, the air would come out of the defroster vent rather than the vents near the middle of the dash. After posting in here about it, we determined that the heater controls were leaking -- more specifically, the selector valve on the back of the heater controls. My dad had a heater control unit from my sister's '86 IROC, so I just took the valves out of that and hooked them up to my unit. Now my vent works just fine -- but I don't have any heat! No matter what position the slider is in, it feels like it's set to full cold.

The cable from the temp slider is properly connected -- I even pulled down the pass side hush panel and I can see that the cable is properly attached at both ends and moves thru its travel just as it should. My coolant is full, and the hoses going in and coming out of the heater control valve under the hood are both hot. There is also vaccuum going into the heater control valve.

My heat worked just fine before I fixed the vent problem, so this is almost certainly related to that. The only other thing I can think of is the 2nd valve -- there's 2 vaccuum valves on the back of the unit. 1 controls whether vent, heater, or defroster is selected. I'm not sure what the other valve does, but I replaced it anyway (I figured if 1 failed, the other probably wouldn't be far behind). Does this other valve have anything to do w/ temp?

 

anybody? Doesn't anybody know if that smaller valve has anything to do w/ heat?