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HVAC controls [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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andrewmoore13
07-19-2008, 05:52 PM
My HVAC controls are ONLY allowing air flow through the windshield defrost part :hissy:. Any ideas on whats wrong or a way to fix this?

Would this be covered under warranty?


Oh by the way... These are the manual HVAC controls... Not the digital.

PROSPHOTO
07-19-2008, 06:54 PM
If you have an extended warranty, it should be covered...depending on the company.

It could be actuators, it could be the control module...it will need to be diagnosed :worried:

andrewmoore13
07-19-2008, 11:50 PM
:( damn.

RayVoy
07-20-2008, 11:09 AM
It's probably a mode door actuator. Try a search, there's a dozen or more threads on this subject.

andrewmoore13
07-21-2008, 09:32 AM
If it's a mode door which one would it be?

Which is to say is it the mode actuator or the defrost actuator? I don't get air anywhere except the defrost vents regardless of where I put the selector on my HVAC controls.

RayVoy
07-21-2008, 05:57 PM
If it's a mode door which one would it be?

Which is to say is it the mode actuator or the defrost actuator? I don't get air anywhere except the defrost vents regardless of where I put the selector on my HVAC controls.Well, as you appear to know, you have one of each. I can not tell which is not working correctly.
I would suspect, that the default setting (total loss of operation) would be defrost. This would ensure air to the windshield when all doors failed, but that's just the way I would design it, who knows what GM did.
I would need to see the physical design and a cycle chart to figure out which one is faulty (from here).
If I was at the truck, I'd find each motor and hold it while operating the control. See which one moves and which doesn't. Hands on testing :).

andrewmoore13
07-22-2008, 03:17 PM
Well, as you appear to know, you have one of each. I can not tell which is not working correctly.
I would suspect, that the default setting (total loss of operation) would be defrost. This would ensure air to the windshield when all doors failed, but that's just the way I would design it, who knows what GM did.
I would need to see the physical design and a cycle chart to figure out which one is faulty (from here).
If I was at the truck, I'd find each motor and hold it while operating the control. See which one moves and which doesn't. Hands on testing :).

good idea


just noticed this was under the 5.3L :duh: