Heater box questions

[elyon]

Does anyone have a schematic of the ac/heater system? Specifically, the vacuum system. Mine acts weird. When I Punch it, the air flow changes from upper vents to the floor. Once the vacuum goes back up it changes back. Also, when all the controls are in the off position, no vent fan running, there is still air coming out of the heater box at the floor. Outside air. Any ideas?

 

[elyon]

Heater box questions #2

Sorry,

1986 K20 Suburban with front A/C only.

 

[British Slave]

 

[British Slave]

I'll add, there is a vacuum resivoir located on the drivers side close to the master cylinder that must be hooked up, it prevents what you are describing.

 

[Keitha]

Check the mechanical link between the manual actuator and the vent door (above pasenger foot well). There is a small, white plastic clip that connects the door to the actuator arm - it frequently brakes.

 

[Fordum]

That is the classic symptoms of a bad vacuum reservoir or check valve. When you punch it, the vacuum from the engine goes to darn near nothing.
If the reservoir has a hole in it, or if the check valve from the engine is bad, you lose all vacuum in the system, and all the actuators release.

I had a '71 T-Bird with full automatic climate control that had two or three canisters under the hood because everything was vacuum controlled.
One of them got a hole in it, and when I was driving along in the hot Florida sun with the AC on high cool, I could punch it and it would switch to full heat.........

Got that fixed quick!

 

[89yimmiJ]

Sorry to hijack...but has anyone used the Vintage Air kits for our trucks?

I occasionally have some of the same vacuum problems and their kit is electronically controlled, no more vacuum lines. And it appears to clean up the underside of the dash and the engine compartment. Just curious.

 

[elyon]

Thank you for the diagram and response. I'll figure this out. Where does this check valve live?