A/C Vacuum problem/ flap door problem.
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Joined: Jan 2013
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From: Louisiana
Car: 88 Camaro IROC, 92 Camaro RS.
Engine: 305 tbi, LT1
Transmission: 700r4, 4l60e
Axle/Gears: 3.43
A/C Vacuum problem/ flap door problem.
When taking the heater core cover off I noticed the flap door next to it was broken(The plastic that holds the door is broken). It doesn't function with the controls at all. Anybody know what this door is for? I have the picture below. Also does anybody have a A/c Control Vacuum diagram? My a/c blows but not as it should. when defroster is selected it still blows through every vent. 
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From: Indianapolis
Car: 1992 Camaro RS
Engine: 1978 L82 355
Transmission: 700R4
Axle/Gears: 3.23
Re: A/C Vacuum problem/ flap door problem.
It's ran by a mechanical cable, not vacuum. All the other controls and doors are controlled by vacuum.
Thread Starter
Junior Member
Joined: Jan 2013
Posts: 49
Likes: 0
From: Louisiana
Car: 88 Camaro IROC, 92 Camaro RS.
Engine: 305 tbi, LT1
Transmission: 700r4, 4l60e
Axle/Gears: 3.43
Re: A/C Vacuum problem/ flap door problem.
Would it be the same cable the Cold/Hot switch is ran by? Also how would you repair this? The door doesnt function at all. When I move the switch from cold to hot I see a cable move right under the heater core but it doesnt move the door at ALL. Im new to all of this. Any help is highly appreciated!
Joined: Sep 2005
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Re: A/C Vacuum problem/ flap door problem.
Right: "hot/cold" is not a "switch"; it controls how much of the air passes through the heater core, by moving that door. "Hot" = all the air passes through the heater, "cold" = all the air goes around it, "anywhere in between" = ... no doubt you get the picture.
The cable end (which you can see in the pic) attaches to a little arm on that door, on the "back" side as shown in that pic.
A "diagram" for the HVAC control would be a waste of bandwidth. All it would be, is a little valve with one input and 3 or 4 outputs, that routes vacuum to any of 3 doors and maybe a valve. The 1st controls whether it's in "heat" mode or "dash vent" mode; then if it's in "heat", another controls whether it goes to the floor or to the defroster; then the 3rd one (labelled "max" in most of these cars) controls whether the blower intake "recirculates" (draws air from under the dash) or draws in fresh air from outside. "Normal" (no vacuum applied to anything, is heat, defrost, and outside air, respectively. Some of these cars, not sure exactly which all, have a 4th vacuum output, that goes to the heater control valve; that valve controls whether hot water is allowed to flow in the heater core. If memory serves, "normal" (no vacuum) for that one, leaves the valve open; and vacuum applied to it, closes the valve and shuts off the hot water flow.
The cable end (which you can see in the pic) attaches to a little arm on that door, on the "back" side as shown in that pic.
A "diagram" for the HVAC control would be a waste of bandwidth. All it would be, is a little valve with one input and 3 or 4 outputs, that routes vacuum to any of 3 doors and maybe a valve. The 1st controls whether it's in "heat" mode or "dash vent" mode; then if it's in "heat", another controls whether it goes to the floor or to the defroster; then the 3rd one (labelled "max" in most of these cars) controls whether the blower intake "recirculates" (draws air from under the dash) or draws in fresh air from outside. "Normal" (no vacuum applied to anything, is heat, defrost, and outside air, respectively. Some of these cars, not sure exactly which all, have a 4th vacuum output, that goes to the heater control valve; that valve controls whether hot water is allowed to flow in the heater core. If memory serves, "normal" (no vacuum) for that one, leaves the valve open; and vacuum applied to it, closes the valve and shuts off the hot water flow.
Thread Starter
Junior Member
Joined: Jan 2013
Posts: 49
Likes: 0
From: Louisiana
Car: 88 Camaro IROC, 92 Camaro RS.
Engine: 305 tbi, LT1
Transmission: 700r4, 4l60e
Axle/Gears: 3.43
Re: A/C Vacuum problem/ flap door problem.
Right: "hot/cold" is not a "switch"; it controls how much of the air passes through the heater core, by moving that door. "Hot" = all the air passes through the heater, "cold" = all the air goes around it, "anywhere in between" = ... no doubt you get the picture.
The cable end (which you can see in the pic) attaches to a little arm on that door, on the "back" side as shown in that pic.
A "diagram" for the HVAC control would be a waste of bandwidth. All it would be, is a little valve with one input and 3 or 4 outputs, that routes vacuum to any of 3 doors and maybe a valve. The 1st controls whether it's in "heat" mode or "dash vent" mode; then if it's in "heat", another controls whether it goes to the floor or to the defroster; then the 3rd one (labelled "max" in most of these cars) controls whether the blower intake "recirculates" (draws air from under the dash) or draws in fresh air from outside. "Normal" (no vacuum applied to anything, is heat, defrost, and outside air, respectively. Some of these cars, not sure exactly which all, have a 4th vacuum output, that goes to the heater control valve; that valve controls whether hot water is allowed to flow in the heater core. If memory serves, "normal" (no vacuum) for that one, leaves the valve open; and vacuum applied to it, closes the valve and shuts off the hot water flow.
The cable end (which you can see in the pic) attaches to a little arm on that door, on the "back" side as shown in that pic.
A "diagram" for the HVAC control would be a waste of bandwidth. All it would be, is a little valve with one input and 3 or 4 outputs, that routes vacuum to any of 3 doors and maybe a valve. The 1st controls whether it's in "heat" mode or "dash vent" mode; then if it's in "heat", another controls whether it goes to the floor or to the defroster; then the 3rd one (labelled "max" in most of these cars) controls whether the blower intake "recirculates" (draws air from under the dash) or draws in fresh air from outside. "Normal" (no vacuum applied to anything, is heat, defrost, and outside air, respectively. Some of these cars, not sure exactly which all, have a 4th vacuum output, that goes to the heater control valve; that valve controls whether hot water is allowed to flow in the heater core. If memory serves, "normal" (no vacuum) for that one, leaves the valve open; and vacuum applied to it, closes the valve and shuts off the hot water flow.
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