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Discussion Starter · #1 ·
I have a 04 LT with auto controls, Some times the AC will blow out the vents and other times it will only blow out the floor, I have a new mode acuator But I am wodering if that is the problem, Any wisdom would be great, Thnks.
 

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Yes sir I have read all the stuff on hvac install and fuse recallibrating. I just find it weird that sometimes the mode works and somtimes it don't. I hate to replace the actuator if it is some other problem..
 

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It could be the actuator, the control module, or the wiring in between the two of them. Very difficult to troubleshoot exactly to the root cause without having a meter on the harness of the actuator while the problem is happening. I've sometimes spliced test wires onto the interesting points of harnesses, and led them out into the cabin so I can measure voltages while the thing I'm interested in is running.

Only if you have a buddy to trade parts with is it possible to solve this without shotgunning, guessing, or troubleshooting deeply to the bad component.

Didn't you say you had a new actuator already? Just put it in. They're not likely to take electrical parts back, are they?
 

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Parts

I am trying to find parts for my Trailblazer. I took it to a dealership and it was diagnosed as the control mudule was bad. May have received a surge when I had to replace the battery. Now I need to get a new one. Any one know where I can find one.
 

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Ebay is often the cheapest. Junkyards are another. On-line discount GM parts places like parts4chevys.com is the third tier. The dealer is the last resort.

This is not a part you can get at the local aftermarket parts stores.
 

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Ebay is often the cheapest. Junkyards are another. On-line discount GM parts places like parts4chevys.com is the third tier. The dealer is the last resort.

This is not a part you can get at the local aftermarket parts stores.
have to replace the module on my 04 T-Blazer LT. I purchased GMpart# 89018778 which is AC Delco part# 15-80567. however this part has a 3-pin connector and the part I'm replacing has 7. My vehicle has manual controls. Can someone help with this?
 

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have to replace the module on my 04 T-Blazer LT. I purchased GMpart# 89018778 which is AC Delco part# 15-80567. however this part has a 3-pin connector and the part I'm replacing has 7. My vehicle has manual controls. Can someone help with this?
I don't know where you're getting the advice to buy GM #89018778 but it certainly wasn't here, unless you read a post and guessed it was the right one for you.

You're confusing the BLOWER speed control module, which you don't have, with the HVAC control module, which is the part in the dashboard with the knobs.

Didn't the dealer tell you the part number you needed to buy?

Anyway, the thing you're looking at with 7 pins is the resistor pack, which is the way the manual control module selects which speed the blower fan runs at. The 3-pin one you bought is the blower fan speed control for the automatic system.

Neither one of these will help fix your problems, which are in the actuator section of the system. You need something like these Ebay listings for under $50:



 

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New Control Module

Hey guys,
Can someone give me the procedure to sync my new control module/head. I've installed the new one and now I only get air from the floor and defroster but not the dashboard vents. I appreciate the help
 

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Find one of my two dozen threads where I mention which fuse to pull and to not touch the controls for a couple of minutes.

If you got a virgin one that had never been powered up before, it may be like the TCCM and need a dealer flash update. Not sure. Almost nobody needs to replace the control module. But your dealer diagnosed it. Maybe they can configure it and make it work.

If you paid them to diagnose the problem, and they screwed up, they owe you.
 
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