Any experience w/ this A/C problem?
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Joined: Aug 2004
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From: North Hills, Pgh, PA
Any experience w/ this A/C problem?
A friend w/ an 1980 is only getting heat and AC air out of the defroster outlets. Is this usually a mechanical or an electrical problem? Are vacuum lines involved?
Thanks for your advice in advance.
Thanks for your advice in advance.
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
There's a flapper door behind the center gauge cluster that controls where air goes (feet/dash/defroster). The problem could be that the selector control is broken so that the internal parts don't move when the control is moved. Could also be a stuck flapper door. The control system is vacuum, but if there is no vacuum the system defaults to blowing at your feet.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
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From: New Hill NC
There is a vacuum valve mounted under the console on the heater-AC control. It is most likely leaking. A common problem with these and you will probably be able to hear it if you listen for it. There is a plastic rivet that holds it together. You can repair it by replacing the rivet or I guess a new valve could be had.
Race Director
Joined: Apr 1999
Posts: 11,520
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From: CORVETTE 77 385 C.I. TEXAS
The problem is that heater is the default position (no vac. or vac. leak) due to being designed in the north. Vent should be default. Very safe bet the problem is 1 OR 2:
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood theft switch into wiper valley. Replacing most of engine side w/ hose will fix. OR
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease or vasoline to fix.
3) If you have a heater, the small hose to heater hose valve underhood probably also needs replacing. Block w/o heater.
PS The design problem comment is not intended to be offensive to any of our northern friends.
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood theft switch into wiper valley. Replacing most of engine side w/ hose will fix. OR
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease or vasoline to fix.
3) If you have a heater, the small hose to heater hose valve underhood probably also needs replacing. Block w/o heater.
PS The design problem comment is not intended to be offensive to any of our northern friends.
Drifting
Joined: Sep 2003
Posts: 1,325
Likes: 6
From: FRANKLIN GA
Maybe this will help. When I had mine down I payed attention to how everything worked. To get air to the defroster the valve on the flapper door has to have vacum on it. If you have a vacum leak in the system it goes to the default setting which is blowing straight down.
So I would say it is either the vacum valve itself is rusted and stuck and not allowing the flapper door to close, the return spring on the door is broken, or the flapper door is stuck in the open position.
So I would say it is either the vacum valve itself is rusted and stuck and not allowing the flapper door to close, the return spring on the door is broken, or the flapper door is stuck in the open position.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
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From: Chattanooga TN
Originally Posted by wombvette
There is a vacuum valve mounted under the console on the heater-AC control. It is most likely leaking. A common problem with these and you will probably be able to hear it if you listen for it. There is a plastic rivet that holds it together. You can repair it by replacing the rivet or I guess a new valve could be had.
