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Discussion Starter · #1 ·
I have a 2003 Chevy 2500HD Duramax. All of a suddent the A/C started blowing hot. :aargh4: Going thru diagnostics all the fuses, high/low pressure switches checked out fine. BTW, this happened after driving through a carwash.

Anyway I came across this over at "dieselplace" dot com.

"Remove the HVAC/ECAS fuse underhood for 30 seconds, reinstall, start the truck, and do not touch any controls for the first 40 secs, allowing the controller to recalibrate and learn. Does AC now work????"

YES, it worked for me. :banana: It sort of reboots the BCM?.? Maybe the carwash made my A/C go haywire because I know it throws off the temp reading on the mirror, maybe that messes with things?

The only thing I don't know is, is this a sign of something going bad? Dunno.

Anyway, I was so happy it worked I needed to share in case anyone else was in need.
 

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Thanks for the info, i have the same truck. Do you know of any problems with the instrument panel not working? Mine will work the first thing in the morning every time. Then when i need to restart it the gauges won't work again until the next morning. Weird!
 

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Discussion Starter · #4 ·
ya, you need to replace the cluster. GM extended the warranty time to cover this. See if your's is still covered. otherwise I have seen classified ads of people fixing them
 

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Our '07 3500 does the same thing. Cruising down the road and the a/c will start blowing hot air. GM doesnt know what is wrong. If you shut the engine off and restart, it will blow cold. Now I just turn the key off and resart it while driving when it does it.
 

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Discussion Starter · #7 ·
Our '07 3500 does the same thing. Cruising down the road and the a/c will start blowing hot air. GM doesnt know what is wrong. If you shut the engine off and restart, it will blow cold. Now I just turn the key off and resart it while driving when it does it.
if the compressor is not engaging try the fuse thing. maybe what you're doing isn't giving the BCM a full "reboot"

I'd say if the compressor isn't engaging and everything else works then it's a computer, or BCM, issue if you can get it to start blowing cold again by turning the engine on and off.

-or-
do you have seperate driver and passenger temp control? if so is only one side getting hot? that's a whole seperate module.

also there are some issues with the flapper doors not directing the right temp air to the right place (ie heated air out the vents) that's another switch or module issue.
 

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My Dad has an 04 Duramax truck and the a/c with get warmer when he is stopped and then blow colder again when he is moving. He has cleaned the condenser and it helped a little, but not much. I'm assuming it has to do with airflow. Maybe his fan clutch is bad or just not moving enough air. I have heard of others with the same truck doing this as well. I may have him try the reset.
 
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