no heat no air movement at all. only hissing sound

1994 GMC ACADIA
184,000 MILES
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DREWDIDDY
  • MEMBER
  • 1 POST
I have no heat in my 1994 gmc jimmy. I have replaced the blower motor. When i move the the heat controls there is a hissing sound coming from the dash?
Nov 11, 2011 at 4:40 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,240 POSTS
The hissing sound is most likely a vacuum leak. The vent door actuators are run by vacuum. Locate where the noise is coming from and I feel you will find a leak. Repair the leak and things should work again.

Let me know what you find. NOTE: You will need the engine running to hear the leak.
Nov 11, 2011 at 5:08 PM
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