Another heater/ac problem


Original poster
Dec 8, 2011
I have a 2004 Envoy with the auto climate controls. A few months ago had to replace the speed control module. Fan kept running after car was shut off. The problem I am having now is the blower with work sometimes and sometimes it wont. Have to turn either the car on and off or the heat or ac itself. Any help would be greatly appreciated.

Ps. This sight rocks compared to the old ad filled trailvoy.


Dec 5, 2011
Did you check the wiring to the relay? It could be bad. The other thing that could be causing the problrm is the Auto A/C control unit they seem to have a history of failures, you can buy a rebuilt one from I-55 salvage in IL for $145.00. If you want to check the blower directly hook power to it and it should spin up.


Lifetime VIP Donor
Nov 19, 2011
Portland, OR
My experience after years on the OS and in my own vehicle was if it wasn't the blower speed module, it was oxidation and overheating of the connector going to it. Getting down there to wiggle things when it's being flaky can often help find it without a meter. But putting a meter to the wiring is the best way to troubleshoot it.

I only read about two instances of a dead control module in the dash. And the members got replacements from Ebay for under $100 IIRC.

Do you have a meter and want to dig deeper, or can you go inspect the harness?


Dec 24, 2011
As said above , check the harness, Mine the red wire was MELTED :lipsrsealed:at the harness, the glove box on the 2006 is not as shown in some of the pictures, it was easier, two tabs on the side and it drops down, hard part was getting all the junk stuffed in there by the kids. I had ordered the resitor from GM parts direct awhile back and held off the job until i had some down time. the inside of the resistor was RUSTED and there was no sign of any water leakage from the outside, I'm thinking condensate? I did need a new harness and ADVAnce was open and hit me for $44. but I now have full use of my AIR!:smile::smile::smile::smile:

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