Ac not keeping up

Aimatdeer · Sunday at 12:38 PM

2024 l8t . Ac has never felt really cold even new. But lately it seems a little warmer. When it gets in the upper 80s and a little more humid it just does not keep up. And sometimes at idle it gets warm. My wife's 2008 envoy is better. My son's 2016 is colder. I have an apointment for a third try Monday the 29th at a third dealer to try and get cold ac before my warranty is out. The first two told me something about so many degrees under ambient temp blah blah blah seemed like they didn't want to mess with me. This was set at low. Max air fan speed high. 87 degrees and a little humid.

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Edited Sunday at 12:46 PM by Aimatdeer

Silverado4x4 · Sunday at 01:44 PM

1 hour ago, Aimatdeer said:

2024 l8t . Ac has never felt really cold even new. But lately it seems a little warmer. When it gets in the upper 80s and a little more humid it just does not keep up. And sometimes at idle it gets warm. My wife's 2008 envoy is better. My son's 2016 is colder. I have an apointment for a third try Monday the 29th at a third dealer to try and get cold ac before my warranty is out. The first two told me something about so many degrees under ambient temp blah blah blah seemed like they didn't want to mess with me. This was set at low. Max air fan speed high. 87 degrees and a little humid.

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AC in home or auto only cool down 15-25 degrees from outside temp, but what will help is to put the ac in recirc mode this will recirc the Inside cabin air rather then trying to cool down the outside hot air, I always have mine in recirc mode.

KARNUT · Sunday at 01:55 PM

4 minutes ago, Silverado4x4 said:

AC in home or auto only cool down 15-25 degrees from outside temp, but what will help is to put the ac in recirc mode this will recirc the Inside cabin air rather then trying to cool down the outside hot air, I always have mine in recirc mode.

I call B.S. when I first moved to Texas my first house would only cool to 80 with the Texas heat. The AC tech said it was normal at 100 degrees outside. I remodeled the house put in a new AC. I could hang meat. My cars may need recirculating to start. Once moving it switches to regular AC and I could hang meat. Living in Texas no one would put up with only 20 degrees difference.

Byrds8 · Sunday at 01:55 PM

Mine is in the shop for the AC now. While it did get cold after a bit, it would take a while to even start to cool the air at all. Turns out the compressor was bad and cycling.

Aimatdeer · Sunday at 02:35 PM

I was using recirc/max air. Especially if it really hot i start out by lowering the front windows a little with regular ac the go to recirculation after a few and rolling windows up. And it does not have the newest refrigerant. It has per the info under the hood r134. Not the new r1234yf.

Edited Sunday at 02:40 PM by Aimatdeer

Silverado4x4 · Sunday at 03:51 PM

1 hour ago, KARNUT said:

I call B.S. when I first moved to Texas my first house would only cool to 80 with the Texas heat. The AC tech said it was normal at 100 degrees outside. I remodeled the house put in a new AC. I could hang meat. My cars may need recirculating to start. Once moving it switches to regular AC and I could hang meat. Living in Texas no one would put up with only 20 degrees difference.

OK you say you could hang meat but what was the actual temp? One of the AC systems job is to remove humidity that we feel on our body your new system removed alot of humidity as that is were the water comes from on the ac coils and that made it feel colder. 80 degrees with high humidity will feel hot vs 80 degrees with low humidity will feel alot cooler.

KARNUT · Sunday at 03:55 PM

2 minutes ago, Silverado4x4 said:

OK you say you could hang meat but what was the actual temp? One of the AC systems job is to remove humidity that we feel on our body your new system removed alot of humidity as that is were the water comes from on the ac coils and that made it feel colder. 80 degrees with high humidity will feel hot vs 80 degrees with low humidity will feel alot cooler.

My house is set at 75. My car at 70. When I have guests the house is at 70.

PunchT37 · Sunday at 04:47 PM

That a/c has got a problem. It should be able to put out at least mid 40`s temp on a day like that.

Vent temp, that is.

Edited Sunday at 05:00 PM by PunchT37

Atlas · Sunday at 07:09 PM

Hard to say what the issue might be. Anything from the ability to cool the AC condenser up front, to blend door issues in the HVAC unit, to refrigerant charge, to compressor issues or issues in the lines.

Report back what the techs find on the 29th.

GM has service publications which list acceptable vent temperatures and AC pressures at given ambient temps and humidity. They probably won't touch the system if it's operating within those ranges.

I'm also surprised to hear your 2024 with the L8T is still using R134a? I was pretty sure the HD's had switched to the new refrigerant around 2020.

PunchT37 · Monday at 12:30 AM

If that guage has a way to adjust [hex on bottom], put that thing in a glass full of ice, put water in, put your gage in, let it sit for 3 minutes or so, and set it to 33 degrees.

Edited Monday at 12:31 AM by PunchT37

Aimatdeer · Monday at 12:52 AM

The thermometer has been in my wife's 2008 envoy, my sons 2016 chevy, my friends 2020 1500 silverado all showing cooler readings. It's not the guage.

asilverblazer · Monday at 03:48 PM

20 hours ago, Atlas said:

Hard to say what the issue might be... to blend door issues in the HVAC unit...

My 2008 started exhibiting similar symptoms, wasn't 'cold' enough. I went through a pretty extensive diagnostic process for a DIY'er with limited OBD access. System evacuation and recharge included.

Noticed one day the passenger side was cold (I'm never over there so took awhile to notice).

Pulled the drivers side blend door actuator out, disassembled it and cleaned it out. Put it back in and did some kind of reset and it fixed the problem.

Long story short, it wasn't the A/C system at fault, the blend door wasn't moving to full cold position.

newdude · Monday at 04:40 PM

On 6/21/2026 at 8:38 AM, Aimatdeer said:

2024 l8t . Ac has never felt really cold even new. But lately it seems a little warmer. When it gets in the upper 80s and a little more humid it just does not keep up. And sometimes at idle it gets warm. My wife's 2008 envoy is better. My son's 2016 is colder. I have an apointment for a third try Monday the 29th at a third dealer to try and get cold ac before my warranty is out. The first two told me something about so many degrees under ambient temp blah blah blah seemed like they didn't want to mess with me. This was set at low. Max air fan speed high. 87 degrees and a little humid.

Seen this gen truck with bad compressors. Also bad blend door linkages which requires replacing the entire HVAC box, but those ones are for getting two different temps driver vs. passenger side (cold on one, hot the other).

EDIT: Performance chart with MAXIMUM outlet temperatures. So depending on ambient temp and relative humidity, you should see temps no higher than the column on the far right out of the vents.

So @Aimatdeer if there are no leaks, the charge of refrigerant is correct, and everything is operational (compressor, temp doors, clutch fan), it might be on the high end of normal per this chart.

Edited Monday at 07:04 PM by newdude

AndrewF · Monday at 06:29 PM

1 hour ago, newdude said:

Seen this gen truck with bad compressors. Also bad blend door linkages which requires replacing the entire HVAC box, but those ones are for getting two different temps driver vs. passenger side (cold on one, hot the other).

Even on a hot/humid day, vent temps with a thermometer should be 40-50F coming out of the ducts when set to the coldest temp.

Is there a spec on what temperatures are acceptable vs. not acceptable? My '24 has fairly weak AC as well but I don't want to waste my time or the dealers time if it is still in spec.

newdude · Monday at 07:02 PM

32 minutes ago, AndrewF said:

Is there a spec on what temperatures are acceptable vs. not acceptable? My '24 has fairly weak AC as well but I don't want to waste my time or the dealers time if it is still in spec.

Just edited my response with a performance chart I found.