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ECC With a mind of it's own

aviator

By aviator
in Ask A GM Technician

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aviator Enthusiast

aviator

Posted
Posted

I've recently traded in a much-loved '02 Avalanche for a used '04 2500 4X4 Crew Cab 6.0 with 27K miles. One of the options it has is the Electronic Climate Control, which is a great idea, but mine seems to have a mind of it's own.

 

I can start the truck, put the ECC in auto mode, set the temp and drive off. For Example, I can set it to 75 Degrees and the dash vents flow warm air, it's 48 degrees outside. a few minutes later, the ECC changes the vents being used from the dash vents to the the defroster The temp doesn't change.

 

Once the system has switched to defrost, I can't get it to change to any other vents, even by taking it out of auto mode and manually selecting other vents and changing the temperature (up or down) but the temp will change; it always blows out the defroster vents.

 

Now, once I turn the truck off, then back on, it will switch the vents to where they are supposed to be according to the read-out. Eventually it will go back to defrost though if I put it back in "auto" mode.

 

What's going on? Does it sound like I have a defective unit or is it supposed to use the defroster as it's main outlet for conditioned air? Sorry for the long post, but I tried to be as detailed as I could.

 

Any help would be appreciated.

71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
Posted

Mine never goes to the defrost vents on Auto. There is a defrost pushbutton on the control module I have to press to get it to go to defrost. Also, when it's in defrost mode, there is a defrost indicator on the screen of the module (looks like a windshield with squiggly lines on it).

Maybe your pushbutton for defrost is sticking on. If you cycle between defrost and auto does the indicator change on/off?

aviator Enthusiast

aviator

Posted
  • Author
Posted

Yes, the indicator changes from on to off and back when I cycle through. I thought the same thing initially, until I saw that the indicator was working properly.

bobcat5544 Enthusiast

bobcat5544

Posted
Posted

GM HAS A TECH SERVICE BULLETIN ON THIS PROBLEM...

 

THE HVAC WIRE HARRNESS TO THE MODE DOOR ACTUATOR MAY BE RUBBING

ON THE INSTURMENT SUPPORT BRACKET AND GROUNDING ITS SELF CAUSEING YOUR CONCERN

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