Ac/heat

[steves1980]

My ac dont blow out the middle vents, when useing heat , i cant get any air blowing out the def.? i know there is a door that should close to send air to the top for def. and air to the middle vents when the AC is on, but where is it and how do i check it ?, all the air is coming out the floor vents.
ty steve

 

[Bob Chadwick]

The system is controlled by vaccum. It comes into the controller in the console and is sent to an actuator on the left side of the air distributor.

 

[steves1980]

Ok got it to open one time, not sure where the( air distributor ) is?, but it did open after i played with the A/C by turning it on then off a few times, it must be getting stuck, i will check into it a bit more.

 

[Bob Chadwick]

I'm not sure what the air distributor is actually called but it is the tower that is part of your ductwork behind the gauges, radio, etc. The air comes out for the heater on the bottom, the vent in the middle and the defroster on the top. There is an actuator on the left side that controls a door that deflects the air.

 

[jz7p6t]

Same Problem on my '80

I had the same problem on my '80 Vette. I had to replace the vacuum lines as they were dry/cracked. They were leaking such that there wasn't enough vacuum to pull the air doors for defrost/ac/heat when changing modes.

Find the main vacuum supply line for the A/C-Heat control and connect a hand held vacuum pump to create a vacuum. Then without changing modes, see how long the vacuum holds, if it doesn't then you have a vacuum leak. When you change modes it might bleed off some vacuum but pump it back down and see if air flow changes with mode changes (def-a/c-heat). If works ok then problem is vacuum supply, probably leaky hose. If it still does not work then you'll have to check lines and mode control valve (located right under the A/C-Heat-Def control. If 2 out of 3 modes work then you might have a stuck/leaky vacuum door valve.

If all your vacuum hoses are original then it's probably time to replace them, kits are available with all required hoses. Saves a lot of headaches in the long run.