Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
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The mode doors in the front HVAC system are vacuum operated. I would suspect a vacuum leak first. Here is a description of operation.
It also has a vacuum pump that supplies vacuum to the vacuum reservoir for the HVAC system. That could also be the problem. Let me know if you want to try and fix yourself and need more info. If you rate me now we can still keep this discussion going.
I do not have a clear diagram of the vacuum routings but I would start by making sure the pump is running and if it is, start from there and inspect vacuum hoses.
Hello. I will try to help you with this. The pump is accessed by removing the air cleaner assembly. I would suggest removing that, and inspecting all the vacuum lines under the hood. It's very possible that one of the vacuum lines has been damaged, corroded, etc and is not supplying vacuum to the actuator. You can disconnect the vacuum line at the pump and apply vacuum with a hand vacuum pump and see if it works then I will provide you with a picture of the vacuum pump, but none of us will have a diagram of all the vacuum lines with their exact routing. You would have to follow the lines and inspect as you follow. The use of a smoke machine would make that job much easier but smoke machines aren't always easy to come by. If you apply vacuum you may hear the leak. There is also a vacuum reservoir under the battery tray. Inspect the vacuum lines to that as well. After inspecting all the vacuum lines, if you find absolutely nothing wrong with any of them then the air door actuator is accessible by removing the instrument panel carrier. I would start with the pump first and thoroughly inspect all the lines. If you need further help please dont hesitate to let me know