Question about 2002 GMC Envoy

1 Answer

Changed battery and now a/c vents won't work, air blows out defroster and floor only.

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  • wayfran Jun 08, 2010

    I wish it was vacuum operated. No, that was too simple. They made the system controlled by electronic switches that are run by the onboard computer system, and when you change the battery you can lose the programming that runs all the electronics in your car. Only GM could figure out a way to screw up your car just by changing the battery, no wonder they are in bankruptcy! There is usually a quick fix available for these kinds of things, like pulling out a fuse or two and chanting the right words to make things work again.

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  • Master
  • 775 Answers

I believe the controls are vacuum operated. when changing the battery, you most likely, however inadvertently, broke or disconnected a vacuum line. when vacuum is removed, the system defaults to the defrost postion to make sure the windshield can be defogged.

Posted on Jun 07, 2010

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flapjack937
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SOURCE: air will not blow out of panel vents

vents are blocked so air is diverted to other vents, check and clean if necessary

Posted on Aug 14, 2008

  • 37 Answers

SOURCE: Heat wont blow through heater or defroster vents

The door in the heater box is most likely stuck. It is located under the dash on the passenger side

Posted on Dec 06, 2008

  • 20 Answers

SOURCE: Heat wont blow through heater or defroster vents

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.

Posted on Feb 23, 2009

  • 37 Answers

SOURCE: PROBLEM WHEN SELECTING THE DIRECTION FOR THE AIR

Sounds like you have a supply vacuum problem. When you lose supply vacuum to the control head it defaults to defrost.

Posted on Mar 13, 2009

  • 432 Answers

SOURCE: All Air Conditioning blows our the defrost vents

Some thing you could look at would be this. The control is usually fed by a vacuum line or small hose thats is connected to your intake manifold.
With a cold engine,look for a skinny vacuum hose that runs from the intake toward the fire wall . It should be going inside the cab and connecting to the A/C vent control.Some times the hose becomes disconnected or splits or cracks due to heat under the hood.
Thats usually the trouble.
I hope this helps you.

Posted on Oct 06, 2009

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1 Answer

I have a 1975 k5 blazer and it blows cold air it worked fine last year but now it only blows cold air even on the defrost setting what can the problem be and how can I fix it?


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