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2006 Chevy Trailblazer 4.2L I6
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Discussion Starter · #1 ·
This is my first time posting to the forum so please forgive me if this isn't the right place to ask this question. I have been using Trailvoy for information since purchasing my 2006 Trailblazer last October. And to my surprise I am having a problem that I cannot find discussed here. As the title states my air conditioner completely shuts off when turned to 5. 1-4 work normally but there's nothing happening on 5. This just started a couple days ago. I did mess with the a/c harness when I installed a Flex-a-Lite electric fan with an AutoCool III controller from autocoolguy.com. But that was a few months ago and this problem just started. Hopefully someone here will know something because I am stumped.

I would also like to take this oppurtunity to thank everyone who takes the time to contribute to this forum. The library of knowledge housed here has been very beneficial for me. I felt I needed to say that.
 

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This is a typical problem that can be from a couple of trouble makers on most GM vehicles.

1. The control that you twist to "5" can burn internally in that switch. It usually ruins the switch and you have to replace the whole thing.
2. The so-called: "module" that is really a printed circuit board that has a bunch of resistors micro-printed on it. There is nothing that is processor'd or any transistors on it at all - therefore it is not a module in the strictest sense.

The HIGH speed circuit will sometimes fail because of excessive current draw by the blower motor and for that, there are many reasons that I'll try to post for you. a) an old dying motor with b) bad bearings or c) a plugged up air filter (if you even have one, that is).

BUT back to your problem ----- you need to drop that card (ne: "module" from the place it lives with special-odd sized deep sockets and you need the ability to stand on your head and find the screws that hold the card in place --- with a mirror --- or someone who has been there before (a guide, if you will).

I --- on the other hand - just ignored the trouble on the #5 failure because if was a bad card (ne: module) - I wasn't going to buy a new card.

I just tapped into the orange wire from the control panel [NOTE 1] that runs the HIGH BLOWER speed and installed a 4-pin relay and sent that output of that relay directly to the purple blower input wire ... from the 12V power strip on the firewall. This is a direct power supply from the battery and is fully fused through the front fuse box.

NOTE ---> one CAN use one of the UPBUILDER 12 VOLT STUDS inside the upper cover - that's inside the under-the-hood fuse box if one wants. It's OK since it's all fused anyway......​

SIDEBAR: The blower only has two wires going into it - the B+ and the Ground. The "speeds" you demand are directly introducing resistors into the circuit to cut the voltage. It's a very cheap way to do it and it should be a PWM-Digital signal by this time in the GM vehicles across-the-board.

Don't worry about any feedback going to the resistor card or even the BCM since it should "see" 12V on it anyway and it's not gonna get surprised by it. Besides that - I cut the wire going back to the resistor board anyway - so it doesn't even matter.​

[NOTE 1] -> you can either cut the wire (no "t" splices, please!) inside the dash area that comes FROM the control panel switch, close to it after you take it out to affirm the wire color - or you can catch that same wire as it goes to the card under the passenger's side toekick area - that's the card that needs the special socket that you don't have in your toolbox - yet.

If you're interested, I can submit pictures - or make a video about it on my wife's 2000 Astro Van - same-o, same-o - only a slight difference.

{check the .pdf below or ... if that doesn't work} please forget that I typo'd that file name <ashamed>

See if this link works for you.

LINK HERE
 

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2006 Chevy Trailblazer 4.2L I6
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Discussion Starter · #3 ·
Thank you for the reply. Unfortunately it is a bit over my head. I'm a DIY guy that likes to tinker with things. While I do know how to solder and use a multimeter, electrical just isn't my forte. I was hoping that I just needed to replace a relay or something like that. Is there anyway you could give me the "For Dummies" explanation?
 

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2004 chevy trailblazer_ls_ext
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It's so easy, even a caveman could do it!

Some people have said that the new one mounts 180 degrees rotated from the old one, but they fit and work just fine. They will only fit one way due to the way they're mounted. Chances are good that it's the resistor. It's a common failure item on these vehicles.
Here's Eric O. having a rough day with one:

If you have a manual control unit your plug will look different, but the concept is similar.
 

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2006 Chevy Trailblazer 4.2L I6
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Discussion Starter · #5 ·
That is very helpful, thank you. I am going to order one as soon as I figure out which one I need. There seems to be a 3-pin and a 5-pin version and I haven't had a chance to see what I got in there yet.
 

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Hopefully it will hold on high speed.

The blower might draw a lot more Amperage than the resistor bank can handle --- especially in high range.

I've always tested the current draw of the blower by a clamp, but that may not be available to you.
You could always insert smaller and smaller fuses inline until you find where they start blowing.​

Prophelactily I usually install a 4 or 5 pin relay to take the load off the new part ---rendering it an old part very quickly.
 
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