No Air Flow from Vents


Old 12-05-03, 09:46 AM
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Join Date: Aug 2000
Location: Pennsylvania
Posts: 124
No Air Flow from Vents

I have a 1994 GMC Jimmy, it has the vortex engine and has about 75,000 miles on it. Problem is the air flow for heat and a/c. Theres heat and air conditioning but, the airflow only comes out where the defrost is. Nothing out of the vents or the bottom. I can put the slide switch in any position but thats the only place where air is coming out. Someone told me that I may have a vacuum hose broke or off. If thats the case, where do I look for it, i have no idea. Or do you think the problem is somewhere else in the system?
Thanks for your help and have a great day.
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Old 12-05-03, 10:47 AM
darrell McCoy
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Look under the hood, either hanging from the bottom side or on an inside fender well. Should be a black plastic ball, size of a soft ball. Start there checking the hose, trace it back. Not real sure, but there may be a small check valve in the line also. You may also have a bad control switch on the dash or a split hose on the back side of it. After you shut the engine off, move the lever to different positions and you should hear a vacumm noise. Roll the windows up so you can have absolute queitness.
Old 12-05-03, 02:40 PM
Desi501's Avatar
Join Date: Oct 2003
Location: Boynton Beach Florida
Posts: 2,207
It's most definately a vacuum supply problem. Defrost is the default position in the absence of controls. A small plastic line will be coming through the firewall to the engine. This line may tee off the the storage canister that Darrell is referring to. That stores vacuum to keep the supply constant. Find the disconnected or broken line. It could be a controller problem but the supply hose is more common.
Old 12-05-03, 02:48 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
The hose falls off the vacuum ball under the hood all the time on these.Hooked under the left rear of the hood.

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