A/C issue

littleal · April 4

I have a 2024HD L5P. I have it to 2 different dealers a total of 3 times. The problem is when you get in the truck and lets say it is 90 degrees in the truck the A/C will not go into full blast. It is set on auto at 71 degrees. This is an intermittent problem and of course the dealer can't duplicate it. I opened a case with GM last fall, Has anyone run into this problem?

chris21 · April 16

It will only go full blast/max cool on auto if you turn the temp down to LO.

nfisherman · May 7

On 4/4/2026 at 12:30 PM, littleal said:

I have a 2024HD L5P. I have it to 2 different dealers a total of 3 times. The problem is when you get in the truck and lets say it is 90 degrees in the truck the A/C will not go into full blast. It is set on auto at 71 degrees. This is an intermittent problem and of course the dealer can't duplicate it. I opened a case with GM last fall, Has anyone run into this problem?

I don’t know if this is your issue. In my ‘26 HD, this is controlled by a Comfort and Convenience setting in the DIC. Mine was bugging me until I found the setting. It was delivered with the max auto fan setting on “medium.” The high setting is an option and there’s a warning that high will be noisier. No kidding! I changed the setting and now it does what I want.

Pryme · May 19

Auto Climate control is too annoying for me. I like the old dummy dial. It just works.

KARNUT · May 19

I have 3 different brands with Automatic climate control. They work. I find myself making very few adjustments. Even my old Avalanche works well as long as the Freon is right. As hot as it gets here it adjust high automatically turns on max air. And adjust down when temperature settings are reached. Some vehicles don’t have dials anymore. Looking over going a mile a minute to make adjustments could be hazardous to your health. Especially when you’re paying attention to your phone at the same time. I don’t like it when I’m dodging people heading to my lane who can’t multitask. Long live climate control.

asilverblazer · May 19

1 hour ago, KARNUT said:

They work. I find myself making very few adjustments.

Same - usually a number between 68-70 in the summer, 72-74 in the winter.

Pryme · May 20

Auto climate tends to run the ac when it’s not necessary. Always hated that. It will run it to clear the window when it’s not needed. I’m not a genius but I’m still smart enough to adjust a knob from the red side to the blue side if I am hot. The more electronics the more issues. It’s apparent daily reading this forum.

asilverblazer · May 21

On 5/20/2026 at 3:03 PM, Pryme said:

Auto climate tends to run the ac when it’s not necessary. Always hated that. It will run it to clear the window when it’s not needed. I’m not a genius but I’m still smart enough to adjust a knob from the red side to the blue side if I am hot. The more electronics the more issues. It’s apparent daily reading this forum.

It 'automatically' runs to control humidity.

KARNUT · May 21

17 minutes ago, asilverblazer said:

It 'automatically' runs to control humidity.

The down on automatic people would probably lose their mind if they found out the AC comes on with defrost.

Atlas · May 21

I don't think the OP's question was ever answered. Sometimes the HVAC doesn't run full-blast to bring the temp down to the set temperature. He gave the example of a 90-degree day (inside of the car is probably ~120+) and the system being set to 71 degrees and not activating fully when he restarts the truck.

I would have suspected the Auto Fan setting too, but the problem sounds intermittent, and it sounds like it does run on high as part of the auto setting.

Atlas · May 21

1 hour ago, KARNUT said:

The down on automatic people would probably lose their mind if they found out the AC comes on with defrost.

Or on modern systems, manual or auto HVAC systems can call for the AC compressor to run in any vent mode or blend door setting based on ambient humidity. Even with the AC button on the controls off/disabled. It's kind of annoying.

I find that I can get along with auto HVAC systems, mostly. But really I'd prefer simpler and manually adjustable fan speed/temp/vent setting knobs. We're talking about the inside of a car, not a multi-story building with many rooms.

KARNUT · May 21

16 minutes ago, Atlas said:

Or on modern systems, manual or auto HVAC systems can call for the AC compressor to run in any vent mode or blend door setting based on ambient humidity. Even with the AC button on the controls off/disabled. It's kind of annoying.

I find that I can get along with auto HVAC systems, mostly. But really I'd prefer simpler and manually adjustable fan speed/temp/vent setting knobs. We're talking about the inside of a car, not a multi-story building with many rooms.

Some vehicles only have touch pads to control their Ac, heat. Looking over while driving over one mile per minute could be hazardous to life. A good climate control system eliminates that. I have three different vehicles with automatic climate control. They work well. As far as a building it be pretty hard to wreck a building, it doesn’t move. Vehicles do. I rarely have to adjust my AC.

Pryme · May 22

17 hours ago, KARNUT said:

Some vehicles only have touch pads to control their Ac, heat. Looking over while driving over one mile per minute could be hazardous to life. A good climate control system eliminates that. I have three different vehicles with automatic climate control. They work well. As far as a building it be pretty hard to wreck a building, it doesn’t move. Vehicles do. I rarely have to adjust my AC.

It takes less than 1 second to glance over to turn a knob. I don’t recall the freeways littered with wrecked vehicles pre auto cc from ppl making deadly adjustments going down the road. Just a little ribbing but really. Not a big deal. Huge tablet sized screens needed to do most things in modern vehicles are way more attention demanding than a basic hot cold dial.

KARNUT · May 22

35 minutes ago, Pryme said:

It takes less than 1 second to glance over to turn a knob. I don’t recall the freeways littered with wrecked vehicles pre auto cc from ppl making deadly adjustments going down the road. Just a little ribbing but really. Not a big deal. Huge tablet sized screens needed to do most things in modern vehicles are way more attention demanding than a basic hot cold dial.

It’s really amusing to me how people will spend a small fortune to buy the latest technology. But automatic climate control can’t be trusted or efficient.

asilverblazer · May 22

20 hours ago, Atlas said:

I don't think the OP's question was ever answered. Sometimes the HVAC doesn't run full-blast to bring the temp down to the set temperature. He gave the example of a 90-degree day (inside of the car is probably ~120+) and the system being set to 71 degrees and not activating fully when he restarts the truck.

I would have suspected the Auto Fan setting too, but the problem sounds intermittent, and it sounds like it does run on high as part of the auto setting.

Must've run him off.

I could have used a little more description of what the conditions were, what the settings on the controls were, plus the setting for "automatic fan speed", what did intermittent mean based on the above? The automatic climate control uses a LOT of inputs to determine what to do, even including the ambient light sensor.