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Author Topic: A/C question  (Read 6876 times)

Offline lawdog49

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A/C question
« on: June 22, 2009, 03:14:44 pm »
Should air blow out of the bottom floor vents if the AC is on max or the regular AC setting?  I didn't think it should come out of those vents unless you have the 'bi-level' switched on.  My 91 blows air pretty hard out of those bottom vents no matter which of the first 3 settings I choose.  Isn't there a valve or something that actuates a door (under the dash or somewhere) to allow some outside air in when you select bi-level?  I'm thinking I am somehow stuck in bi-level mode, and it's causing me to not get much forceful air out of the dash vents, nor as good at cooling as it should be because of warm/hot outside air being introduced(and I just had the system charged after repairing the rear AC hoses, pressures were brought up to where they are supposed to be).  I really don't even have any use for the bi-level mode.
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1991 GMC Suburban 1500   -   5.7/AT/4x4/TBI

Offline Captkaos

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Re: A/C question
« Reply #1 on: June 22, 2009, 03:59:27 pm »
No it shouldn't be blowing out the bottom.  It sounds like the doors are stuck. 
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Offline VileZambonie

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Re: A/C question
« Reply #2 on: June 22, 2009, 06:05:08 pm »
The heater outlet should only blow when selected to: Bi level or heater

The defroster should receive air flow when set to: Defrost, bi-level, and defrost

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Offline lawdog49

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Re: A/C question
« Reply #3 on: June 23, 2009, 01:10:13 pm »
i didn't think that was right, so ideas on a fix?  is that door controlled by a mechanical valve somewhere?
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1991 GMC Suburban 1500   -   5.7/AT/4x4/TBI

Offline lawdog49

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Re: A/C question
« Reply #4 on: June 29, 2009, 04:28:09 pm »
anybody?  how do I check/fix that stuck door?  I didn't think I had one in the kick panel area, so I'm guessing this door is inside the heater box or something?
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1991 GMC Suburban 1500   -   5.7/AT/4x4/TBI

Offline VileZambonie

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Re: A/C question
« Reply #5 on: June 29, 2009, 04:34:43 pm »
Do you have a factory service manual? It gives you more detail then I can describe to you. The mode controls have too many variables and charts for me to post them. Just make sure the vacuum controls are connected correctly. Try to manually operate each control and see if it's working correctly.
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Offline lawdog49

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Re: A/C question
« Reply #6 on: June 29, 2009, 05:52:01 pm »
no, but I can find one.  I had a guy install a new heater core- before that the AC would run you out.  Afterwards, it barely cooled, then apparently developed a leak in the rear hoses.  So, now that I have the system leak free and charged, I am getting all this air blowing out the bottom vents- so I think when he installed the heater core, he screwed up something there letting the floor vents blow air all the time that is at least partially pulled from engine compartment.
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1991 GMC Suburban 1500   -   5.7/AT/4x4/TBI

Offline Captkaos

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Re: A/C question
« Reply #7 on: June 30, 2009, 05:35:44 pm »
If you had the heater core replaced I would check the hoses are still connnected and make sure everything is connected right.  Did a shop do the replacement?  If so I would take it back and tell them your AC is blowing on your feet now and not out the vents.
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Offline comp

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Re: A/C question
« Reply #8 on: July 01, 2009, 04:00:49 pm »
does it bloww to the floor with just the fan on high ??? bet its a blend door
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Offline VileZambonie

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Re: A/C question
« Reply #9 on: July 01, 2009, 04:19:46 pm »
The blend door is for hot and cold, not mode.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline lawdog49

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Re: A/C question
« Reply #10 on: July 10, 2009, 09:44:40 pm »
it is apparently blending hot and blowing out both upper vents and floor vent.
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1991 GMC Suburban 1500   -   5.7/AT/4x4/TBI
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