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 HVAC controls "hissing"

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melonman26



Posts : 8
Join date : 2015-09-11

PostSubject: HVAC controls "hissing"   Mon Sep 14, 2015 2:13 pm

Hey guys, any common problem known for vacuum controls leaking on the '93 Caprices? I am hearing a high frequency "hiss" whether fan is on or off and is not radio hiss either. I just got the wagon and noticed it right away and the whole ride home. I have yet to dig into her but assume that it uses vacuum controls for HVAC-Anyone hear of this issue? Do you think I am heading in the right direction?

Thanks!
Larry
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Fred Kiehl

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Posts : 4307
Join date : 2009-11-13
Age : 68
Location : Largo, FL 33774

PostSubject: Re: HVAC controls "hissing"   Thu Sep 17, 2015 9:31 am

It could be a number of things. A loose or broken line, broken valve, or even a bad vacuum motor.
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melonman26



Posts : 8
Join date : 2015-09-11

PostSubject: Re: HVAC controls "hissing"   Mon Sep 21, 2015 8:57 am

Was able to pinpoint a blue (purple) what appears to be a / the supply line that is teed. It goes to back of fan speed selector control switch/valve and is teed to pass on somewhere (maybe to vacuum tank). I pinched off where it passes on and by initial appearances all controls seem to work at both low and high engine vacuum condition. defrost, heat, cool-floor, face etc. I can't seem to find a vacuum diagram online that shows routing clearly. Looking for any links that may show where this is teed off to (what I am pinching off).

Most diagrams mention a black line for main vacuum supply.

Thanks for any assistance- and no I obviously don't have a service manual yet!)

melon
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Fred Kiehl

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Posts : 4307
Join date : 2009-11-13
Age : 68
Location : Largo, FL 33774

PostSubject: Re: HVAC controls "hissing"   Mon Sep 21, 2015 10:33 am

Here is the hose diagram:

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melonman26



Posts : 8
Join date : 2015-09-11

PostSubject: Re: HVAC controls "hissing"   Tue Sep 22, 2015 8:35 am

Thanks Fred!!
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