Hi guys. I have an '85 T/A with no A/C, just regular heater.
The problem is even when I have the heat turned off completely there's still hot air coming out the floor heater vents.
The heat/cool slider on the controls seems to move properly going from heat to cool in the defrost and dash vents but only hot air on the floor.
I've talked to a few other 3rd gen owners with the same problem.
any thoughts?

Thanks Steve.

 

The heater core still heats up with the engine coolant. Now I used a shut off valve and allot cooler in the car. However, when I turned it back on in the fall my haeter core started to leak. Does not make sense because I only shut off one side so I only interrupted flow. Not pressure. Now some of the 91-92 3rd. gen had a water control valve controlled by the control panel in the car. Vacuum operated.
BTW, I still use the valve after replacing the heater core. No problems for 3 seasons now.

 

It was on 1989 cars, my Firebird has it.

A pic of the valve.....

 

Thanks guys. I was kinda hoping for some info on the actual heater box and doors inside it. Is it possible that the foam gaskets around the doors have rotted away letting hot air around them?
The heat only comes out on the floor, not the dash vents or defroster vents.
I had thought about putting a shutoff valve in the heater hose but was warned against it as it might make the heater core start leaking, as happened with Gordon's above. I wonder if putting a valve in both hoses would keep the pressure in the heater core from changing and possibly leaking?

 

With all due respect to Gordon, I believe his heater core leak was a coincidence, and not directly caused by using a heater control valve. Otherwise, all cars with heater control valves would have heater core leaks in the fall after not using the heater all summer.

I do believe, as you theorize, that for whatever reason the door that controls the flow of hot air from the heater is not blocking off the hot air.....