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Former GM Tech and parts
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Hey, I'm just trying to help. Working on these things on my own for 12yrs now and being a former GM tech and parts guy has its advantages sometimes lol

If you looked up that line for the suburban, you could probably get the correct one for it and have the full ac system operational even
 
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Like always I’m late to the party! Haha I ended up falling asleep before the rain stopped 😂😂
 

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2004 Suburban 2500 LB7
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Discussion Starter · #24 ·
If you looked up that line for the suburban, you could probably get the correct one for it and have the full ac system operational even
So the conversion used the LB7 engine bay fuse box, so it doesn’t have the fuse location for rear A/C. I’d have to chase down the wiring for the rear unit and then interface it with the LB7 fuse box. Not to say I won’t try down the road, but for now the front should be fine.

even though I’m late there’s mine
No worries! Still appreciate it! Just double confirms the line I just ordered should get me going down the right path.
 

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2004 Suburban 2500 LB7
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Discussion Starter · #25 ·
Alright, update.

Got the new A/C line earlier this week and had some time to install it today. Fit perfect. Wasn’t too bad of a job, but I had to take a lot off to get the line fished into place. Haven’t had a chance to get it serviced and filled, but here’s to hoping!

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2004 Suburban 2500 LB7
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Discussion Starter · #26 ·
Another update...

Just got my A/C fully serviced and filled with the new line installed. Everything is brand new except the compressor and the condenser. Had dye added so hopefully if it still has a leak I'll know where it is, but the only places it would be from are the compressor shaft O-ring seal or the condenser itself! Let's hope not.

Alright - Compressor still won't cut on like normal. (Rewind a bit) The diesel performance shop I took it to months ago did install a temporary switch to the compressor itself to manually turn it on and off when they attempted to fill it before (with the old incorrect line installed). With using that previously installed temp switch to control the compressor, it blows awesome!

Obviously I want it to work like factory and not on a manual switch. I realize running the compressor constantly on a manual switch will shorten it's life. I do cycle it on and off - which is why I'm so determined to get it to work properly, cause it's annoying. So, I researched some more and did some troubleshooting. Here's where I'm at - mind you, I did this all on my lunch break, lol.

-Checked pretty much every single fuse in the entire truck. All check good. - NO Compressor power.
-Swapped A/C compressor relay with Horn relay. - NO Compressor power. (Horn works perfect with the old A/C compressor relay, so both relays check good)
-Tried to jump the low pressure switch and nothing.... - NO Compressor power.

I'm left to trace the entire low pressure switch pigtail wiring to inspect it for damage unless I'm missing something else to check?? Where does this pigtail lead to?? Straight to the compressor?

Any other thoughts on this guys?
 

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Discussion Starter · #27 ·
Ok, jumped the A/C relay (87 to 30) and it kicked the compressor on. Don’t know how I missed checking this. 🤦🏻‍♂️

What now!? Is the HVAC control unit bad?
 

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Do you have the manual HVAC or the automatic? Manual would be to roll the knob the auto is where you put in the digital temp you want?
 
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2004 Suburban 2500 LB7
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Discussion Starter · #30 ·
Do you have the manual HVAC or the automatic? Manual would be to roll the knob the auto is where you put in the digital temp you want?
I have this type…manual I’m guessing.
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I also remember the shop mentioning something about it possibly triggering off of the power of the radio headunit? Since it’s in a “locked” condition, it could be effecting the A/C triggering?? I don’t have the code to unlock the factory radio, but about to put in an aftermarket one soon.
 

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Yes manual. Does your blower motor work at all? Do you have all 5 levels? Or is it just always hot when its blowing? Does your HVAC panel illuminate at night or is it always dark
 
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Discussion Starter · #32 ·
Yes manual. Does your blower motor work at all? Do you have all 5 levels? Or is it just always hot when its blowing? Does your HVAC panel illuminate at night or is it always dark
Blower motor works on all levels. The drivers side blender door motor is inop so I have it removed and it’s zip tied temporarily to the coldest setting. Illuminates at night as well.
 

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Discussion Starter · #33 ·
Went to the local junkyard and swapped in another manual climate control panel and still nothing. Either that one was bad too (which I doubt 2 would be bad) or I have to look into the tuning. Putting this on pause for the moment as the A/C works great on the manual switch for now. I may re-tackle this next season along with trying to re-integrate the rear A/C back to factory specs.
 

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Went to the local junkyard and swapped in another manual climate control panel and still nothing. Either that one was bad too (which I doubt 2 would be bad) or I have to look into the tuning. Putting this on pause for the moment as the A/C works great on the manual switch for now. I may re-tackle this next season along with trying to re-integrate the rear A/C back to factory specs.
Wait. What do you mean it works on the manual switch? Sorry i haven't logged on in a few days
 

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Discussion Starter · #35 ·
The diesel shop I had it at installed a temp switch directly to the compressor until I could troubleshoot it. It has been cooking hot so I agreed to it.
 

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Ok well that changes things a bit

Is this wired to a toggle switch now? Or ignition hot?
 

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Toggle switch
The reason you can have the high side port and low side port on the same run is that the orifice tube is located in front of where the two lines join at the nut fittings. The pressure drops as the refrigerant turns from liquid to a gas and lets the pressure drop.
 

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Discussion Starter · #39 ·
This is still bothering me to no end!

Here’s where I’m at.

  • Heat coming just from drivers side vents.
  • AC button doesn’t trigger the AC compressor on the HVAC control module.
  • Drivers side temperature slider on the HVAC control module doesn’t control the drivers side blend door actuator.

EVERYTHING else on the HVAC module works as it should.

Drivers side blend door actuator physically works when going through the recalibration sequence. I have it unbolted and just hanging there to watch as I troubleshoot.

Swapped 3 different junkyard HVAC control modules in and no change. Possibly all bad modules? Maybe.

What am I missing here!?!? Are all these issues linked together and pointing to a bad HVAC control module?? What’s my next step?? I’m hearing all the Dorman replacement HVAC modules are crappier than the OEM. Do I Amazon one and take a chance??

PLEASE HELP!! LOL
 
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