Weird AC problem. 2010 Yukon *SOLVED*

[Sir_Hiro]

When I bought the truck it was winter. My Brother works in Hvac so we checked the Freon and it was empty. We filled it and the air worked wonderful for a while.
Now that its been hitting 70-80Fs here its stopped working. Compressor isnt short cycling and according to my Cheapo Gauge the pressures are within spec. I did hit the valve on the high side and it had freon.
What else is there to check?

TLDR: Compressor is running but no cold air, Pressures good

 

[Doubeleive]

When I bought the truck it was winter. My Brother works in Hvac so we checked the Freon and it was empty. We filled it and the air worked wonderful for a while.
Now that its been hitting 70-80Fs here its stopped working. Compressor isnt short cycling and according to my Cheapo Gauge the pressures are within spec. I did hit the valve on the high side and it had freon.
What else is there to check?

TLDR: Compressor is running but no cold air, Pressures good

are the hvac lines under the hood cold after it has been running for a bit? if so then the issue is likely a blend door actuator.

 

[Sir_Hiro]

are the hvac lines under the hood cold after it has been running for a bit? if so then the issue is likely a blend door actuator.

Ice cold. I do have the Auto Climate control I should have mentioned. But if I go to max hot..It'll melt your face off.

 

[Doubeleive]

Ice cold. I do have the Auto Climate control I should have mentioned. But if I go to max hot..It'll melt your face off.

the hot/cold blend door is the one under the glove box, you have to pull the kickpanel under the glove box (3) 7mm, you can remove the 2 farthest ones and then just push it down out of the way the 3rd one is hard to get to. then the actuator is bottom dead center uses (2 or 3) 5.5mm bolts, when you adjust hot/cold you should see that actuator rotate, if it's not moving that would explain why you have heat only. if you pull the actuator you can move the door manually and then see if you have cold air.

 

[rdezs]

Also if you have the rear AC, see if it's blowing cold while the front is warm. That will verify it's the blend doors up front.... Or the signals they are receiving from the HVAC module. (Which often is traced to a bad cabin temperature sensor)

I miss the vehicles with cable operated controls. Was so much more reliable.

 

[Sir_Hiro]

Update* front ac lines are ice cold however rear ac lines are ambient temps. Im starting to suspect that its just low on charge and my cheapo low pressure guages isnt right.

 

[Sir_Hiro]

the hot/cold blend door is the one under the glove box, you have to pull the kickpanel under the glove box (3) 7mm, you can remove the 2 farthest ones and then just push it down out of the way the 3rd one is hard to get to. then the actuator is bottom dead center uses (2 or 3) 5.5mm bolts, when you adjust hot/cold you should see that actuator rotate, if it's not moving that would explain why you have heat only. if you pull the actuator you can move the door manually and then see if you have cold air.

I will try that later. Working on the C10 till its cooler out

 

[Doubeleive]

Update* front ac lines are ice cold however rear ac lines are ambient temps. Im starting to suspect that its just low on charge and my cheapo low pressure guages isnt right.

the rear lines won't be very cool no matter what, not externally anyway that is normal, the lines are just too far away from the compressor to be cold to the touch
maybe.... after it has been running for a good while they might feel slightly cool, they may even sweat condensation, but not like the lines up front.

 

[Sir_Hiro]

the rear lines won't be very cool no matter what, not externally anyway that is normal, the lines are just too far away from the compressor to be cold to the touch
maybe.... after it has been running for a good while they might feel slightly cool, they may even sweat condensation, but not like the lines up front.

Interesting. I've never really messed with HVAC systems. If it wasnt for the Little one I wouldnt bother fixing it. But we need the AC for the long family roadtrips. I'll verify the Actuators today.

 

[Sir_Hiro]

Ordered some proper 3 Way AC Gauges, Should arrive today. Will be able to hopefully verify pressures and go from there. Compressor started short cycling yesterday when I was running it.

 

[Doubeleive]

Interesting. I've never really messed with HVAC systems. If it wasnt for the Little one I wouldnt bother fixing it. But we need the AC for the long family roadtrips. I'll verify the Actuators today.

I know on mine the XL I have reached under there and felt the lines after it had been running a good long time and they did not feel very "cool" and my system is working correctly
maybe the short wheel base is different.
once you have determined if the actuator is working correctly then put a cooking thermometer in the vent and see what it shows. should show around 43-44deg if it's better than that your lucky, my old 03 silverado would freeze you out that thing cranked out about 35deg or somewhere around there never had a better system.

 

[Sir_Hiro]

I know on mine the XL I have reached under there and felt the lines after it had been running a good long time and they did not feel very "cool" and my system is working correctly
maybe the short wheel base is different.
once you have determined if the actuator is working correctly then put a cooking thermometer in the vent and see what it shows. should show around 43-44deg if it's better than that your lucky, my old 03 silverado would freeze you out that thing cranked out about 35deg or somewhere around there never had a better system.

Update #2? Verified Actuator function. It moves according to temp settings. Got my Gauges late yesterday so after work I will be hooking them up and checking pressures.

 

[Doubeleive]

Update #2? Verified Actuator function. It moves according to temp settings. Got my Gauges late yesterday so after work I will be hooking them up and checking pressures.

weird, i guess check the high/low. if it turns out to be low/low when you fill it use a can with dye

 

[Sir_Hiro]

weird, i guess check the high/low. if it turns out to be low/low when you fill it use a can with dye

I'm thinking its Low, According to my new gauges with. The Low side is about 30PSI low and high was about 20PSI accordin to the chart in the OEM Repair Manual. I'll stop today and pick up a couple cans try again.

 

[rdezs]

I would replace the air dryer and the expansion valve..... It's a great time to replace the system gaskets/seals .... Apply a vacuum and make sure it holds for 30 minutes..... Then refill the system.

 

[Sir_Hiro]

I would replace the air dryer and the expansion valve..... It's a great time to replace the system gaskets/seals .... Apply a vacuum and make sure it holds for 30 minutes..... Then refill the system.

Eventually I will do a more indepth check of the whole system, But I have a couple family road trips coming up and just need the AC to work for now.

 

[Sir_Hiro]

Final update. It was low on charge, moral of the store. Dont buy the cheapo chinese guages, but the meduim grade chinese gauges, however that does mean i have a leak somewhere.

 

[rdezs]

Next time you're under the vehicle, look underneath and behind your AC compressor pulley for any dark green residue. If you see any, it's starting to leak from the AC compressor shaft. (And they're not very expensive, unless you go to a shop where they Jack the price way up. RockAuto is your friend here)
The valve cores for the high and low side are normal replacement items when you evacuate the system, they also tend to leak as they age. You can get all the gasket and seals you need plus the valve cores for less than $25. Even the condenser core in front of the radiator is inexpensive. Pinhole leaks are pretty common from road debris. Nothing wrong with using one of the cans of 134a that have the sealer in them. They actually do a good job on extremely minor leaks, except for if it's the compressor shaft.

 

[PG01]

I went through the same thing last summer? Two years ago? CRS anymore… moral of the story, use the right tools for the job…. I was being lazy and didn’t feel like getting the good gauges from my bsmt… the ‘cheap’ gauge said it was full…. Short cycling, uncool air, out of laziness i ordered a pressure switch ( i know i know 10 steps into the bsmt to get the gauges but no…… ordering something online was easier) I think i put 2 cans in or something like that and shes cool now…

 

[Sir_Hiro]

I went through the same thing last summer? Two years ago? CRS anymore… moral of the story, use the right tools for the job…. I was being lazy and didn’t feel like getting the good gauges from my bsmt… the ‘cheap’ gauge said it was full…. Short cycling, uncool air, out of laziness i ordered a pressure switch ( i know i know 10 steps into the bsmt to get the gauges but no…… ordering something online was easier) I think i put 2 cans in or something like that and shes cool now…

Yep, i had a single low pressure gauge from years ago and that kept saying it was good. So i ordered the 3 way set and dumped 2.5 cans into it. Now i got ac