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A/C Vacuum Controls

WyrTwister on Tue July 15, 2014 10:27 PM User is offlineView users profile

Year: 1991
Make: Chevy
Model: Caprice
Engine Size: 5.0L
Refrigerant Type: R134A
Ambient Temp: 95F
Country of Origin: United States

I am in the slow process of restoring this car ( belonged to my late Father ) . The A/C is one of those chores .

The controls have a bottom lever that goes from cool to heat . I think this has a mechanical cable that operates a blend door ?

There is a vacuum operated " hot coolant " valve , under the hood . I am guessing it is also operated by the bottom lever ?

Looking at a diagram of the control unit shows a double hose that , if I recall , is labeled as going to a water valve .

When I move the bottom lever , I hear a noise that sounds like it may be a blend door opening and closing . So , at least the blend door may be working correctly .

There is also an upper lever on the control unit that goes from max A/C on the left to defrost on the right . It seems , no matter what position that lever is in , part of the air is coming out the defrost vent & part coming out the dash A/C vents . Some may also be coming out the bottom heater vent ? Have not checked .

So , this control is not working properly .

The diagram of the control unit shows a 5 hose connection , which I figure are 5 vacuum hoses ?

Before I start messing inside and under the dash , I wish to verify that I truly do have good vacuum going to the control unit . Does anyone have a drawing / diagram if the vacuum system for this car ? And I would appreciate info on where the source vacuum line for the A/C controls , plug in to receive engine vacuum ?

Any other info or tips would be much appreciated . :-)

Thanks ,
Wyr
God bless

WyrTwister on Thu July 17, 2014 6:26 AM User is offlineView users profile

Looked around under the hood . Found one tired looking hose & replace it . Did not solve the A/C problem .

Found a hose that tied in with a bundle of wires , headed towards the firewall . But that is about all I could tell .

Unless I make a discovery , under the hood , it looks like I am going to have to investigate under the dash . :-(

God bless
Wyr

WyrTwister on Thu July 17, 2014 12:40 PM User is offlineView users profile

There was a vacuum check valve at that same area . Hoped that was the problem . Checked it and is OK .

Next step is probably going to investigate under the dash .

God bless
Wyr

wptski on Thu July 17, 2014 2:03 PM User is offline

Your vacuum might be a little big/noisy for the task, maybe a hand vacuum pump? You probably can't hear a vacuum leak but what about a little air pressure and listen for a hiss?

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