AC stuck on defrost???

zach1990 · April 15, 2013

Ok guys my 2000 sierra started only blowing from the defrost vents yesterday. It still changes from hot to cold and the 1-5 speed control works properly. Read in some other topics to check the blend door actuater so I pulled it up on autozone.com to check prices and noticed there are 8 of these things! I pulled everything apart and I found 2. One by the blower motor which I'm thinking is the hot/cold blend actuator and another close to the steering column that I can't identify. Is this my culprit? If so which actuator is it? Part number?

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txab · April 16, 2013

A re-calibration may fix you up. Try disconnecting the battery for
a few minutes. Reconnect it. Or remove the HVAC/ECAS fuse for a minimum of 10 seconds.

Re-install the HVAC/ECAS fuse.

Then turn the key to the on position, but
don't start. Don't touch the HVAC controls. Let them do whatever that
want to do. Air flow may change outlet points during this time. Wait
about 1 minute. Turn key off. Opening and closing the door can
make a difference as the vehicle controls see this as "cycle"
completion. Next start the vehicle and drive it a short distance and see
how it performs. You may indeed need to replace an actuator.

bossier62guy · April 16, 2013

See attachment

Try AC Delco 15-72505, GM 52473356, Dorman 604-113

hvac.pdf

zach1990 · April 16, 2013

Thank y'all! Got the battery disconnected right now and if that doesn't work the diagram will be a huge help! Y'all are the bomb!

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bossier62guy · April 16, 2013

I just added some part numbers as well....the Dorman units seem to be the cheapest though.

Here's a little lagniappe for you...

http://www.gm-trucks.com/forums/topic/101322-air-comes-out-of-defrost-vent-only/

zach1990 · April 16, 2013

Well no go on the battery and fuse :'(

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bossier62guy · April 16, 2013

Doesn't surprise me....I tried it once on my 02 and it didn't work. Had to change a temp actuator.

zach1990 · April 16, 2013

I well I just hope the first part I buy fixes it. This could get expensive quick...

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zach1990 · April 16, 2013

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bossier62guy · April 16, 2013

It'll be good man....I'd say you were lucky to get that many years out of it myself. Here are some removal/replacement procedures for you. Just make sure you don't power the thing up before it's installed (several people here have done that) or else you'll be buying another one.

modeactuator.pdf

bossier62guy · April 16, 2013

And if you haven't checked out the link above it's basically from a guy that had an identical problem with his truck.

zach1990 · April 16, 2013

Good deal ty. It'll be about 2 weeks before I do this. I'll be sure to post the results. Thanks again!

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zach1990 · May 5, 2013

Well this problem just compounded. As of this morning the air only comes on when u put it on 3 (no other function works) and once its on its on. The only way to shut the air off is to turn off truck and put the selecter on 5 (this really confused me). I'm at a loss here. FWIW I still haven't fixed the defrost problem but idk if its related

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bossier62guy · May 5, 2013

check your fan wiring very closely for signs of overheating....

and no, it's not related....

zach1990 · May 9, 2013

check your fan wiring very closely for signs of overheating....

and no, it's not related....

I was looking for a gimped wire and couldn't find anything then after unplugging it at the blend actuater and checking those wires and plugging it back in it went right to work. Idk loose connection maybe???

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