85 Heater Control Valve Question

[carhopper]

I have an 85 AOD/CFI with no heat. When the car is warm, the inlet to the core is very hot, and the return is moderately warm which tells me the valve is not opening. I don't see a valve in the engine compartment so I have to assume it's under the dash. Can someone please help me troubleshoot this valve before I pull everything apart. What actuates the valve, vacuum or electric. Is it actuated by by moving the heater lever because that works. Where do I start. I bought a Haynes manual but it's not very helpful.

 

[Bills89GT]

Im not totally sure about your 85 but on my 89 there is no valve like you are looking for. there is a valve that changes the direction of the air flow through the air box but coolant is always flowing through the heater core. the valves are mounted on the side of the air box behind the dash, one is cable operated and the others are vacuum operated. Here is a picture of my buddys 84

 

[carhopper]

Yep that looks just like mine. The vacuum is for outside air and the other damper is cable operated. Maybe I'll pull the hoses to the core and make sure it's getting fluid through. Thanks a lot.

 

[ID89GT]

Maybe your blend air door is stuck? That was the problem on mine, pop your glove box down and move the door by hand and see if you can feel a temp change. It turned out my cable had a kink in it so it wouldn't move past a certain point. Swapped out cables and then it worked fine

 

[carhopper]

The core was completely blocked blowing either direction. I filled both hoses with pure flush and let it sit then blew it out with compressed air. I did this several times and eventually it flowed water without pressure. Once I get it back together, I'll run some flush again and let it heat up. I don't know how well it will work, but at least I should get some heat.

I just hope I didn't create a leak. Worst case, I had to change the core anyway so what did I have to lose.

This will also fix the problem where my temp gauge jumps from zero to about 160 when heating up. The return water to the sensor is through the heater core. Maybe it will help the cooling system efficiency a bit too.

While I was taking apart the hoses, the "T" fitting broke and I had to order one.

 

[carhopper]

I got it back together and heat works great with no leaks. This thing must have set for a long time by a previous owner without much use for that to solidify like it did. Anyway, on to a couple of electrical problems and I'm 100% fixed.