my mother in laws chevy blazer is acting up. it has the automatic climate control. no matter what, it blows very very hot. i can switch it to manual or automatic, it doesn't matter. when i'm playing around with the controls for which vents the air will blow out of, once or twice it momentarily blew cold air, then went back to super hot again. what does that sound like to you fellas?
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Dec. 28, 2011 5:57 p.m. belteshazzar SuperDork
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Dec. 28, 2011 6:13 p.m. 93gsxturbo HalfDork
Blend door is not actuating.
There is a reset procedure that basically involves pulling the batteries or the fuse for the controller for 10 minutes and forcing a relearn that way. When you put the fuse in you should hear a few motors under the dash moving, stopping, moving, and then stopping again.
You can also look for a broken mechanical bit in the HVAC system. Have someone work the control from full hot to full cold and back again and see whats moving.
To do any further diagnosis you need a GM Tech II scanner or another scanner capable of displaying the commanded positions and actual position of the blend motors. Watch for the one that command position and actual position are out by more than a few percent. Watch the commanded position when actuating the knob for temperature control to make sure it moves to rule out a bad knob. The controls rarely fail but the motors love to.
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Dec. 29, 2011 3:36 p.m. novaderrik Dork
this is why i've grown to hate late models vehicles- you should not need an oem scan tool to fix the heater..
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Dec. 29, 2011 3:41 p.m. pete240z SuperDork
93gsxturbo wrote:
There is a reset procedure that basically involves pulling the batteries or the fuse for the controller for 10 minutes and forcing a relearn that way. When you put the fuse in you should hear a few motors under the dash moving, stopping, moving, and then stopping again.
The Trailblazer's have a similar problem (it has 5 of these) when you swap in a new battery. I had one go bad and I spent 6 hours under the dash one day changing it out. I still can't get the controller right. Rumor is the dealer pulls the dash out to fix them to the tune of $1,000+.
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Dec. 29, 2011 3:48 p.m. pete240z SuperDork
http://forums.trailvoy.com/showthread.php?t=60944&highlight=dash+vents
Can't speak for the 1998 Blazer...........
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Dec. 29, 2011 7:35 p.m. 93gsxturbo HalfDork
Pete, is one of the motors sticking and binding and causing the issue? Shouldnt be any reason to pull the dash other than to verify operation of the systems? The reset procedure does move the drives to the roads less traveled, so to speak. So its possible something is jammed or out of range.
If you are coming to the Milwaukee area, let me know, I have a Tech II and would be happy to take a look at it for you for some cheap beer.
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Dec. 29, 2011 9:02 p.m. pete240z SuperDork
93gsxturbo wrote:
Pete, is one of the motors sticking and binding and causing the issue? Shouldnt be any reason to pull the dash other than to verify operation of the systems? The reset procedure does move the drives to the roads less traveled, so to speak. So its possible something is jammed or out of range.
I had a bad motor and I failed to mark it's location when I bought a replacement. You can change these without removing the dash but patience is key.
