Question about 1979 Pontiac Firebird

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1980 firebird esprit

I have a yellow vacuum line under the dash that is broken off/disconnected at it's plug in end. The other end is connected to the heater/ac controls. It is an ac car. The vacuum lines come from the controls and swoop toward the passenger side and are taped together so I assume it's in the correct general area. Probably 10 years ago I swapped out the original dash pad and put a 77 pad in, so I'm sure I caused the problem with all the ductwork out and such. Also one visible vent door is only closing part way when I switch the controls.

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Try and check all of your flapper doors and make sure they all have vacuum lines connected to them. These vacuum lines control different flapper doors depending on what setting your A/C and heating system are set at. For instance defrost opens the top flapper doors in your dash, bi-level opens the lower flappers and mid-dash flappers. What I would recommend is first checking each setting. Turn the car on and first run defrost. If both flappers are open then those are ok. Then run regular A/C, make sure the flapper doors are open to all the mid-level vents, if that is ok move on to the lower level setting and check that. This will help you pinpoint what doors are having issues. When you find the one that is not opening or not closing this will be the door and that is the one that does not have the vacuum hose connected. Let me know how everything goes.

Keep me posted - Tech101

Posted on Jun 27, 2008

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The yellow vaccum line is supposed to be routed thru the fire wall and to manifold vaccum to control your vent positions it goes thru the fire wall behind and a little up from your right valve cover and should have a vacuum resorvoir in the system

Posted on Oct 22, 2008

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