2000 GMC Yukon XL A/C Issue

JTC95 · May 2, 2018

Hello! Hopefully this is the right forum for this, but I have had an issue with my A/C system come up recently.

I have a 2000 Yukon XL 4wd SLT with the 5.3 and the computer climate control system, it has almost 250k on it now and has been a great truck, but the lack of A/C going into the warm weather now is not pleasant.

I realized that the a/c compressor was not turning on, tried recharging the system but the gauge I have, which i trust, shows the system at optimum charge. I then unplugged my low-side a/c plug and tried jumping it, which made the compressor turn on and the air did I think get colder, though I only had it jumped for a few moments to avoid damage. But this did make the compressor turn on, nothing else would.

My question is where do I go from here? Does anyone have an idea of why the compressor will not turn on normally? I have checked all the fuses and none are blown, and as far as I can tell all the relays are good too. I am guessing electrical fault somewhere, but there are no other faults with the HVAC controls. A few years ago the heat would not work, but after leaving the battery unplugged for I think about a day it came back when I re hooked the battery.

Thanks for any suggestions you may have,

John.

Doug_Scott · May 2, 2018

What do you consider "good" pressure? Depending on ambient temps low side should be 35-45 @ 70 degrees F and high side should be 145 - 165 @ 70 degrees F.

I have never seen a gauge that can show if correct volume of refrigerant is in the system. I have seen gauges that will have green zones that highlight preferred range. And those ranges are with compressor running. Short the low side pressure switch again and this time leave it connected to get proper readings. Did you happen to check pressures before adding refrigerant? The manual air system holds about 4 cans of refrigerant from empty.

JTC95 · May 3, 2018

I will try this next, would you happen to know how to reset that low-pressure sensor? I did this same process in a 99 Firebird before and to reset that sensor all I had to do was unhook the positive terminal for about 10 minutes.

Thank you.

Doug_Scott · May 3, 2018

I have heard that the auto air conditioning will completely reset if the battery is disconnected for a set length of time. Don't recall how long, but I am sure taking off the cables then having lunch is likely more than long enough. Personally I will not remove the positive lead first simply to avoid having my wrench or ratchet welded to the chassis when it slips and shorts the positive to ground(chasssis/fender). Removing the negative first gets around that possibility. DC current demands both positive and negative connected to perform any electrical procedure. If you want you are free to re-attach the ground after removing positive, just remember to remove it before re-attaching positive after lunch.