AC/Heater Controls and Air Flow Problem

[84Elky]

Need some problem solving help in understanding what is going on with ’84 El Camino. Have read many threads here but none seem to describe my problem. All control panel settings direct air where it should go, but with one problem – there is always air coming out of the heater vents, even with everything turned off (both levers are fully to the left). Some detail below but necessary:
- Car does not have vacuum controlled heater control valve.
- No vacuum leaks
- The heater vent air volume is car speed dependent; with more air blowing the faster the car is going.
- With everything off, the air is hot as if the heater is on.
- The AC/Heater door is, I believe, fully closed to block heat. That is, the threaded rod attached to the AC/Heater door is pushed in toward the firewall as far as it will go (I’ve pulled the rod out of the holder clamp and have confirmed this, but have no way of visually confirming the door is actually moving although it appears to be).
- When AC is on (set to Max, Normal, BiLevel or Defrost), the air from the heater vents is cold.
- The re-circulate door is closed on Max and open on all other settings.

Any ideas on what I can check or do to stop the heater vent air flow? Need to fix this because it really gets hot in the car when AC is off.

 

[carmangary]

On my 79 Cutlass, the fan is always on even when everything is set to off EXCEPT when the outside air temperature is below 60 or so degrees. That is how it was designed to work. If you are getting hot air, then your heater flap is not closed or not all the way closed. If it is closed, air will bypass the heater core.

 

[84Elky]

carmangary --- Agree about the fan, but my air flow is car speed dependent and is not coming from the blower fan -- the higher the speed, the more heater vent air flow. That does not make sense – especially from the heater vents -- and would seem to indicate there is flap/door other than the heater flap/door that is open somewhere. But I have no idea what to look for or how to test it. Surely there is something that should prevent large volumes of outside air from entering the car when everything is off and the blower switch is in the bottom position.

What you say about the heater flap/door does make sense. So how can I test to determine if the door is fully closed? I’ve disconnected the rod from the temperature control cable and pushed the rod I’m assuming is attached to the heater door/flap in toward the firewall as far as it will go. It feels and sounds like the door is fully shutting. Shouldn’t this block heated air, because “in toward the firewall” is the same direction the rod is moved with the cable when the temperature slider is moved to the left toward ‘Cold’?

I’m still searching for how to find & fix this thing.

 

[carmangary]

Check for a hole somewhere. Maybe hot air from your engine compartment is being blown into it as you go down the road.

If no hole, maybe the seal around your heater control flap has rotted off and it leaking badly. You would need to open it up to check. It isn't too hard to open it up once you get through all of the sealant holding the top on. But, that old plastic cracks easily if you force it.

 

[Veltboy618]

I'm posting this from my iPhone so the pic might come up small. Maybe this can help you figure out where it's coming from or which door you need to fix.

 

[84Elky]

Thanks guys! veltboy314 - That pic is helpful. carmangary - By 'open up', you mean removing the blower motor cover? And I'll be able to see the heater door controlled by the temperature lever?

 

[Veltboy618]

Thanks guys! veltboy314 - That pic is helpful. carmangary - By 'open up', you mean removing the blower motor cover? And I'll be able to see the heater door controlled by the temperature lever?

I have the blower motor cover off on the car I'm building so I can take pics of the inside if you want me to.

It sounds like the door is not closing all the way & the faster you go the more air is being pushed though the heater coil then into the car from the vent outside your car by the windshield.

 

[84Elky]

veltboy314 - Would really appreciate the pics. Thanks in advance!

 

[carmangary]

I can't remember if you can see the flap by removing just the fan but it would be an easy thing to try. I was actually referring to removing the entire top of the heater box.

 

[Veltboy618]

veltboy314 - Would really appreciate the pics. Thanks in advance!

No prob. I'll have them in the morn