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Discussion Starter · #1 · (Edited)
I don’t know if I’m posting this in the right place but any help with post/truck is greatly appreciated. This is my first diesel truck.
I have an ‘01 Chevrolet Silverado 2500HD extended cab long bed Duramax/Allison, had for about a year and a half. I believe it’s the LB7.
Upgrades/Mods
Mishimoto radiator, Mishimoto trans cooler, ram cold air intake, Brake controller-bags in the rear w onboard air compressor
I’ve done maintenance and small fixes as I’ve owned it, wheel hubs, balls joints, tie rods, shift selector, rear main seal, fuel filter/upgrade, every fluid etc.

Since I’ve owned the truck the A/C hasn’t worked. I’ve got the time and money now so I thought I would try and fix it.

The pump never kicked on when the a/c or defrost buttons were on. I took it to a shop they tested my pump,fuses,relays,and the system itself. Everything is charged and works, but only when they give the pump direct power manually. I replaced my fan/temperature control knobs etc in the cab. And now I don’t know what to do. One other weird thing is that the fan only blows inside the cab when it is set to 4 or 5. Does not blow at all when on 1,2,or 3. I expected that to change with the new fan/temp control unit but it did not. The controls all seem to work in the sense that the a/c and defrost buttons light up when pushed, the air/warm air will blow at the feet section-dash section, and defrost section when you switch the knob to the different settings. Only 1,2, and 3 settings don’t work on the fan.
My next idea was to either trace and replace the wiring from the a/c compressor to the fuse box or replace the whole fuse box or replace my blower motor but I’m hoping it’s something stupid easy I’ve overlooked.
Thank you in advance!

Me and the mrs towed a 37’ 2016 travel trailer over 3,000 miles and enjoyed every minute of it! This truck may not have a/c but she never left us stranded or in a bad spot.
 

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Does your compressor turn when the HVAC is turned on? Or are you just having a fan problem? If fan problem only, there is a resistor that precedes the fan motor in the circuit under the dash . This blower fan resistor failure is very common on Chevys.
 

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Discussion Starter · #3 ·
Does your compressor turn when the HVAC is turned on? Or are you just having a fan problem? If fan problem only, there is a resistor that precedes the fan motor in the circuit under the dash . This blower fan resistor failure is very common on Chevys.
I purchased a resistor today to hopefully fix the fan not blowing on the 1,2,and 3 setting. The compressor does not come on at all and doesn’t come on unless you give it direct power (jump it) I’m not certain how to explain the direct power process but basically they have this tool that clamps on the battery terminals or somewhere idk exactly and then you touch it to the a/c compressor and it gives it direct power bypassing the fuse box altogether. I may be wrong with that exact explanation but that’s the general gist.
 

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Discussion Starter · #6 ·
Did you get this figured out?
I was able to get it figured out but haven’t had the last part put in yet. They spent a few hours under the hood and what they came up with is the wiring for the a/c that goes from the pump itself, through the firewall into the dash, and back out to the fuse box under the hood, has a short in it. From what they explained the wiring runs through the wire harness so you essentially have to do the whole wire harness. I instead opted to just run new wiring for the ac and haven’t dropped it back off at the shop yet because I’ve been using it to move.
 

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I was able to get it figured out but haven’t had the last part put in yet. They spent a few hours under the hood and what they came up with is the wiring for the a/c that goes from the pump itself, through the firewall into the dash, and back out to the fuse box under the hood, has a short in it. From what they explained the wiring runs through the wire harness so you essentially have to do the whole wire harness. I instead opted to just run new wiring for the ac and haven’t dropped it back off at the shop yet because I’ve been using it to move.
Good to know, thanks for the update
 
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