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billet
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896 Posts
Discussion Starter · #1 · (Edited)
So I'm out of ideas so far on this. Long version below with not relevant information because of my usual ramblings. I have searched and read a ton thus far, but yeah...cliff notes below that lol

Background: 03 NBS Sierra 1500, was a floor console truck, replaced with a NNBS jumpseat console (the one with 3 cup holders lol) years ago. I've ensured I have the correct blower motor resistor for the truck. I had previously had the symptoms in 2011 or 2012 that led me to simply replace the resistor pack, has been completely fine since then. A few weeks ago was blowing AC on 4 (i almost always have it on setting 4 for some reason) and then bam stopped blowing, no blower motor function on any setting whatsoever. Was running between 2 eVet's for our...porch cat who was in a crate so windows down and go. Stopped at AutoZone, grabbed resistor and as I'm headed home it blower started functioning again. Chalked it up to I'll deal with it later and that it was the resistor again. Fast forward a week or so as the truck had sat on driveway (I work from home, and was typically driving my wife's car to take her to her PT appointments for her back or my car to run around in) go out, start truck, thinking nothing of it, AC blowing (still on setting 4), come back out to take daughter to local small town fair and....no AC blowing, AC is on, but no blower motor functionality on any setting period at all. We enjoyed our time at the fair, went to the park and all that fun stuff. Next day I go to deal with the fiasco and start replacing parts.

Cliff Notes:
Replaced blower motor resistor
Replaced HVAC control unit (refurb'd unit)
Have power at 5 pin plug that goes into blower motor on all settings from HVAC control.
Do not have power out of resistor from 2 pin that plugs into blower motor on any fan speed and no fan speed functionality at all.
5 pin plug that goes into blower motor is not burnt or melted and looks ok (?)
Tested blower motor itself out of truck (jumper wires, booster box)
Checked 40a fuse underhood, "looks" ok.
Related? service 4wd and ABS light brake / warning kicked on, will not go into 4wd at all.

There has to be something I'm obviously missing that's going to be one of those "I'm a dumbass" moments here.

 

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truck have a cabin filter? they really slow air flow down to nothing when dirty
 

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billet
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896 Posts
Discussion Starter · #4 ·
So, after doing some more digging and keyboard research, I learned that having the service 4wd and ABS lights pop on along with zero blower motor functionality leads back to the orange wire that provides power (stemming off the ignition switch) and dumps into the back of the fuse block inside the truck having burnt, the terminal being jacked, or the ignition switch going back itself.

In my case, i found I had power at orange, but no power at the 30amp fuse (HTR/AC). I popped the plug pictured below off, inspected, popped out orange, other than the slight discoloration of the wire, nothing else visible found.

Plugged back in, and voila no service 4wd or ABS light and full blower motor functionality. Popped plug back off and on a few times to make sure I had everything seated, added some dialectic grease and reassembled for final (lol) time. I did pickup an ignition switch just to have as it's the OEM piece (truck has 200k).



 
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