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2004 chevy trailblazer_lt
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286 Posts
Discussion Starter #1
Ok so I am experiencing some intermittent fan issues with my heater and with pretty constant 0-20 degree weather that is no good. So I was looking around and saw issues with blower motor control modules and blower motor resistors. Can anyone tell me which issue I am having so i can order the right part? I do have the automatic hvac controls and even if I turn on the manual control the fan does not respond but it will come on just not at any certain time. Thanks for the help!

Nate
 

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2002 gmc envoy_slt
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110 Posts
Hey I am on the forum looking for a solution to this exact issue. It only started in the cold weather and when we hit a bump in the road.
I will appreciate hearing feedback on this.
Thanks
 

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2003 chevy trailblazer_ltz
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35 Posts
Probable Fix For Blower Motor Problem

I had the same intermittent blower motor problem on my 2003 Trailblazer, and I replaced the Blower Motor Control Module and it fixed the problem. I also have the auto HVAC. The blower motor would run for a while even with the ignition off. It would not work in any manual settings. I purchased the Blower Motor Control Module at my local Chevy dealer and paid $90.00. It was easy to replace. I hope this helps!

Dave
 

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2002 gmc envoy_slt
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110 Posts
Hi Dave and thanks for the response. Is the Blower Motor Control Module the actual motor, or the resistor, or another part entirely?
I don't want to purchase the wrong part and not be able to return it because it's an electrical item.
Appreciate it,
Happy New Year!
Here's a link to a pic of what I've been calling the resistor.
http://webcaps.ecomm.gm.com/servlet/com.entigo.acdelcocatalog.servlet.ProcessImageServlet?languagecd=EN&countrycd=CA&user=InternetUser&mfgname=ACDELCO&prodlinecd=15&acpartnbr=15-80186
 

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2003 chevy trailblazer_ltz
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35 Posts
Hi Jay, the blower control module is installed in the lower area of the heater plenum and it looks just like the picture you provided. The local Chevy dealership first tried to sell me the resistor type module for a manual system which looks different and is a lot cheaper. Have a nice day.

Dave
 

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Western Canada Chapter
2003
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6,411 Posts
Always check the wiring harness at the time you replace the resistor or module. The wires have been known to have an issue with breaking and causing much of the same problem as you describe. The dealer may tell you to replace both if you replace the resistor/module as they say the problem can be related.:m2:
 

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2002 gmc envoy_slt
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110 Posts
Hey more great advice. To clarify I assume you mean the plug that goes into the module. If its not looking to good and needs to be replaced is it a matter of soldering in the new piece or does it come as a whole length which gets plugged in on both ends?
 

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2004 chevy trailblazer_lt
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286 Posts
Discussion Starter #9
I looked at the plug on my TB and it just seems like it isn't staying tight in the module. I can move it around and turn it on and off. Is that just the module or the plug itself??
 

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2003 chevy trailblazer blower control module

where is this located i believe this is my problem. i have automatic setting. My blower will run low no matter what i put it on in manual settings. I can restart the car and sometimes get it to go to high or it will go to high whenever it wants to.
 

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2003 chevy trailblazer_ltz
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35 Posts
The blower control module is installed in the lower area of the heater plenum right next to the blower. I paid $90 for the blower control module (auto HVAC) at my local Chevy Dealership. Good luck!

Dave
 

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2004 chevy trailblazer_lt
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286 Posts
Discussion Starter #13
Yes it is behind the glove box. There is a panel below the glove box that you will take off and can see up to where it is.
 

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2006 chevy trailblazer_ls
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89 Posts
I had a similar problem. My heat was working only on speeds 1-3. I spent a hour reading these forums and was able to determine it was the resistor pack that was spoke of. Brought the resistor pack this mourning from the dealership for about 60. Installed it in about 25 min. Would have been done a lot sooner but the harness had actually melted in a few places so it took a while to pry it off. Will be buying a harness from the junk yard eventually and soldering it on. The dealership wants 200 for the harness. I would like to thank everyone on this form. The pictures and description of where it was located was great.
 

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2005 chevy trailblazer_ls
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Hello everyone, i been having this same problem with the resistor and the wiring harness. My harness is also burnt at the end and melted the resistor. So does anyone know why the harness gets so hot that it melts the resistor, and how can i fix this? Thanks in advance for any help and replys.
 

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2004 gmc
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26,181 Posts
Harnesses get hot because of high current going through the connector that hits a bit of oxidation or atmospheric corrosion that causes a bit of resistance. Resistance causes voltage loss that turns into heat. Heat that goes on and off with the vehicle running and being turned off causes small amounts of thermal expansion and contraction that in turn causes more and less contact force inside the connector that in turn causes a higher resistance and that makes for more heat that makes the entire problem worse and worse until the connector finally heats up enough to melt plastic, wire insulation, or discolor the wire. It's a snowballing phenomenon once it begins.

Gold plating reduces these effects, but not the tin plating on most automotive connectors.

I've been studying aging electronics systems for most of my 35-year engineering career, and connectors are a specialty of mine.
 

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2006 chevy trailblazer_ls
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89 Posts
Eventually I was going to replace the harness but this seems as if that will also only be a temporary fix. To fix the problem do I need to redo the harness with gold plating?
 

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2004 gmc
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26,181 Posts
99.9% of vehicles don't have a failure like this. I wouldn't worry about gold plating. But I always laugh at the audiophiles who think they get better performance out of gold-plated audio or video connectors. Unless it's a real thick plating, it scratches right off of the high spots in the connector when they first put it together. And it's only the high spots (microscopically) that are touching. But that's another technical debate for another forum. :yes:
 

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I'm wondering if this is the same issue that this thread is talking about. The fan will not work on settings 1,2,3 but will work on 4 and 5. This is the latest problem with this junk box. Every week it is something else.
Thanks :hissy::hissy::hissy::hissy:
 

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2004 gmc envoy_sle_xl
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151 Posts
I dont mean to hijack the thread, but this looks like it could be a good time to ask about the rear heat and cooling.

Where is the resistor pack for the rear blower. It seems like my rear blower is intermittent and I am guessing that this could be my problem...right? Secondly, I also seem to have problems getting air to blow from the top vents and the floor. I hear the blower working, but can't feel the air from the top or the bottom. It's like the air is getting lost somewhere. Any ideas?

thanks for the help and apologies for a potential hijack.
 
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