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Discussion Starter · #1 ·
I have a problem with my A/C

2002 Trailblazer LTX

Driver's Rear AC Control Switch stopped responding today - Rear AC vents are staying on, all the time. Including with the engine off (key out).

Had to disconnect the battery tonight to make sure it would start in the morning.

Air is blowing cold when it's on otherwise

I'm not a mechanic but I'm hoping someone here can help.
 

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Discussion Starter · #3 · (Edited)
fuses

I found a J-case Fuse #35 referenced in the owners manual - is that the one your talking about? it's in the forward (engine compartment) fuse box. not the rear one.

...........

Update - pulled the 35-40 fuse out this AM - yes that turns off the blower, however you can still feel the air coming out of it (cold with the key in, hot with it out)
 

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Discussion Starter · #5 ·
Update

After I pulled the fuse this AM I pulled the battery off, went and showered so I could take the truck in to the Dealer. My neighbor came over and I was trying to show him what was going on...............

It stopped doing it.

Of couse it didn't start up again before I got to the dealer and I said no thanks to a $99 diagnostic fee.

I looked in my manual and couldn't fine the 13-30 fuse you were talking about. I'll take another look tonight when I get home. I think it was there - but wasn't referenced as a "Blower Motore Fuse"

Hopefully it doesn't start blowing while it's sitting out in the parking lot.
 

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Yes, it's critical to know WHICH blower is running on. The front blower is behind the glove box, and the blower for the rear (on your short wheelbase vehicle) is in the front dashboard area near the driver's right foot, buried behind the HVAC control module.

If you pull underhood fuse #35, that only kills the front (main) blower. If you have digital controls, then it's likely that your blower control module (about $80) is bad. Less likely is that the main HVAC control module (with all the buttons on it) is bad.

If you really have the rear blower motor running, not the front, then pulling underseat fuse 36 should kill that. There is no separate relay in the circuit for the rear blower motor, just the rear HVAC control module in the console.

So which of your blowers is really running on? Front, rear or both?
 

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Discussion Starter · #7 ·
Just ran out there to grab something.

First thing I noticed when I opened the glass hatch on the back was a whining noice eminating from the back right quarter panels. I have an LTZ - it's the longer wheelbase, could the blower be back there?

Started the truck up turned on all the AC vents - blew hot air in the back for a few seconds before it cooled off. Turned the truck off, all blowers turned off - no noise. ????
 

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Sorry, sorry. I'm used to seeing long wheelbase listed as EXT, not LTZ. That system definitely locates the rear blower to the right rear quarter panel. And it's fused by rear fuse block #13. A failure of the control processor next to the motor could cause it to stay on. Item #5 in this drawing: ACDelco #15-72813

So have you been having both front and back blower problems?

 

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Discussion Starter · #9 ·
Ok,

The only problems I've been having have been with the rear. My external sensor is bad and it always tells me it's 50 degrees outside (about 90 right now in New Orleans) but I read on what to do in another thread for that.

Front panel AC is running cold as it should. This all happened last night / this morning. The only other thing I may have forgotten to mention is that the rear AC ran for an hour or two on my drive home last night even with the switch set to 0. When I got home is when I realised that it would NOT turn off. That and the rear controls were unresponsive at best - didn't appear to make a difference what buttons I pressed.

So I pulled rear fuse 13 - which definately stopped the rear AC, at least now I feel like my battery is not going to be dead when I go out there to go home from work. :)

Nate sent me a PM and may have the part that it sounds like I need.
 
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