Hva/c Question

MikeSki1 · 06-26-2008, 10:20 AM

I dunno which section to ask this in, but I was hoping someone here could help. My dash vents work only at an idle or no acceleration, as soon as I get on the gas they only blow through the defrost vents. I'm sure it is some sort of vacuum problem, but where should I start. I have already replaced the selector switch with all of the colored hoses on it.

neo71665 · 06-26-2008, 06:28 PM

Sounds like some of the vac lines got swapped around.

layinlow88 · 06-26-2008, 06:48 PM

possibly....theres also vac lines under the hood....and one right next to your right leg on the floor....next to the floor vent on the drivers side

the reason it switches to the defrost is because of lack of vaccum in the lines....GM defaulted this into the trucks for safety reasons....anytime the vent doors lose vaccum it will always blow on the windshield to defog it

so basically....you may have the selector hoses on right....but theres either a hose not connceted somewhere...or theres a huge leak....try running max ac on high....then kill the truck and listen all around your dash for suction noises

MikeSki1 · 06-26-2008, 08:06 PM

Thanks guys

lesterl · 06-27-2008, 10:11 AM

could be bad check valve or canister

06-26-2008, 10:20 AM	#1
MikeSki1 Shreveport S-Clusive Join Date: Oct 2002 Posts: 910 Location: Shreveport, La User is: OffLine	Hva/c Question I dunno which section to ask this in, but I was hoping someone here could help. My dash vents work only at an idle or no acceleration, as soon as I get on the gas they only blow through the defrost vents. I'm sure it is some sort of vacuum problem, but where should I start. I have already replaced the selector switch with all of the colored hoses on it.
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06-26-2008, 06:28 PM	#2
neo71665 4x4 v6 blazer Age: 28 Join Date: Oct 2004 Posts: 3,097 Location: rison arkansas User is: OffLine	Re: Hva/c Question Sounds like some of the vac lines got swapped around.
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06-26-2008, 06:48 PM	#3
layinlow88 GET LAYED!! Age: 19 Join Date: Jun 2007 Posts: 5,085 Location: Camden, AR User is: OffLine	Re: Hva/c Question possibly....theres also vac lines under the hood....and one right next to your right leg on the floor....next to the floor vent on the drivers side the reason it switches to the defrost is because of lack of vaccum in the lines....GM defaulted this into the trucks for safety reasons....anytime the vent doors lose vaccum it will always blow on the windshield to defog it so basically....you may have the selector hoses on right....but theres either a hose not connceted somewhere...or theres a huge leak....try running max ac on high....then kill the truck and listen all around your dash for suction noises Last edited by layinlow88 : 06-26-2008 at 06:50 PM.
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06-26-2008, 08:06 PM	#4
MikeSki1 Shreveport S-Clusive Join Date: Oct 2002 Posts: 910 Location: Shreveport, La User is: OffLine	Re: Hva/c Question Thanks guys
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06-27-2008, 10:11 AM	#5
lesterl Wire Splicin Fool :-) Age: 29 Join Date: May 2008 Posts: 1,347 Location: Kansas City Area User is: OffLine	Re: Hva/c Question could be bad check valve or canister
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