Question about 2006 GMC Envoy Denali
I can fully switch between defrost, dash, floor vents and combinations of all. i started having an infrequent problem where i would switch to the dash vents and i could hear the air rushing, but apparently it wasn't opening the door to the dash vents. usually next time i turned the truck back on it would be fine. now, no matter what i do, i can't get air to come out of the vents but when switched to dash, can still hear air rushing.
Mode doors. control center. obstruction. vacuum leak.... some gm systems have a vacuum valve where the supply comes into the cab
i have found it split or broken . its bigger than a thimble and has 3 ports. normal operating design allows for defrost only when theres a loss of full vacuum. the location i have found it: has been passenger side, at the main bulkhead (or firewall) and behind or under a cover, often the RF leafscreen by the wiper area.
since your vehicle has so many components and ways to go wrong,
you may have to start disassembling to operate and watch the mode doors move. that is, once supply is verified and corrected as necessary.
if a two stage motor is half working, it can also do things like this.
now , as new as this one is, and electronics may be a factor, you may need to self test the control or use a scan tool on the bcm.
are you starting to see where a service manual is necessary?
a shortcut may be to get the recalls and tsb's for your vehicle prior to diagnosis. automotive databases are available free at most public libraries. ask for help, printing your findings is around a dime a page.
but dont print the whole thing. we need all the trees we can save
Posted on Apr 14, 2014
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Posted on Jan 02, 2017
SOURCE: defrost vent door wont open
sounds like you have a vaccum leak or a blockage in the blend door area of the HVAC system most of the doors are controlled by vacuum if not by vacuum on of the servo motors that control the blend door is not functuning properly. Hopr this is helpfull
Posted on Jan 17, 2009
Is it a new vehicle? I had a new vehicle that had the same problem. Answer was that the holes weren't punched out of the vent.
Posted on May 23, 2009
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