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Discussion Starter · #1 ·
I have a 2003 chevy Trailblazer EXT, V8-325ci 5.3L. It has a front and rear ac. We just spent close to 2k in overhauling the ac system.

The front AC control knob has levels from "0" (off) to #5 (highest). However, when I put it on 5 it does not work. It works from 0-4.

The rear ac only works if the front knob is on the "R" and even then it only works for 5mins.

What could be the problem?

:thx
 

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The front ac speed control is a very common gm problem.
You will need a new blower motor speed control module (auto HVAV), or a blower speed resistor assembly if you have the manual HVAC.

Try a search, there is a ton of info on the site.

The rear, of course, should work from the front control, or from the rear control when the front knob is at R.
This also sounds like the blower motor speed control assembly (there is only one for auto or man systems). Or, possibly a bad blower motor.

Welcome to the site
 

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Discussion Starter · #3 ·
RayVoy,

Thanks for the info.

If my A/C controls are not digital does that mean I have the manual HVAC?

As for the rear it worked either when it was controlled in the front or when the knob was at R. Now it only comes on when the front knob is at R and it only stays on for about 5 mins and then cuts off. To get it started I would need to turn off the car, wait about 10-20 mins and then start the car again and it the rear ac would come on as long as it was set between 1-3. However, it would turn off after 5 mins.

Do you have any ideas what search words I could use to find the information I need in the forums?

I did some searches but the terms I used were general and the results were too many to count.

I appreciate your help!:thumbsup:
 

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Yes, that would be the manual system.

Yep, I hear ya, the right search word is a big help.
Try blower resistor.

The rear problem is a new one, I might look at the speed control unit, or a poor ground.

The speed control unit is mounted at the blower motor (both front and rear). You can get to the motor in front by getting under the dash and behind the glovebox. The one at the rear is behind the side panel that is behind the rear passenger door.

The rear motor speed control is a digital unit (only type used at rear), we don't have a lot of trouble with it, but it could be overheating. The motor it's self could be over heating, or the ground (it would be a black wire) might be loose.
 
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