A/c weird issue

[Tf79]

Especially in hot temps, unless on the highway all the time.

In Tennessee, hottest it’s been is probably 96ish. Highway at 55ish everyday but won’t overheat if I’m in traffic or in the city

 

[justirv]

2004 Yukon Denali. Already did an evac and recharge, no leaks with the dye we installed. A/c on first start when it’s hot won’t work, compressor kicks on but kicks off. Rev it to 1k, it noticeably kicks on for 15 seconds, cold air, then kicks off, warm air. One truck starts moving it works great ice cold. When I come to a stop it works, not as cold but it’s definitely working. When I get home and put it in park it works. Turn truck off and back on it works. Button turns compressor on and off correctly. It only doesn’t work when it’s hot out and on first start up. I’m so lost lol anyone have this issue before?

Confirmimg your rig has front and rear air? Did you weigh in your charge after a good and proper vacuum test? I have found my front/rear setup really touchy on weight, where adding an ounce or two will "all of a sudden" kick it on, and all is good. Definitely get some gauges on it, record low and high pressure, check ambient air temp, and refer to gauge psi/temp to verify you dont have non-condensibles in there. Let us know what you find.

 

[Tf79]

Confirmimg your rig has front and rear air? Did you weigh in your charge after a good and proper vacuum test? I have found my front/rear setup really touchy on weight, where adding an ounce or two will "all of a sudden" kick it on, and all is good. Definitely get some gauges on it, record low and high pressure, check ambient air temp, and refer to gauge psi/temp to verify you dont have non-condensibles in there. Let us know what you find.

Will do thank you

 

[OR VietVet]

Dealer did a evac and recharge. Changed the schrader valves. Nothing else wrong in their opinion. Ambient temp is around 90 when it happens. I’ve been watching a bunch of videos trying to learn how this system operates so I can see what else might cause it. No overheating issues, and fan clutch has been swapped. It only happens when I first start the car after work. Overnight it’s fine. You think they didn’t do the evac correctly?

So, let me get this straight. It only happens after sitting all day in the heat at work but when the vehicle sits in cooler temps overnight, it is fine? A/C does not blow cool/cold air immediately, especially after sitting in the sun/heat. It takes the air in the vehicle and absorbs the heat and gets rid of that heat at the condenser and recycles the air/refrigerant back and it is cooler. As the process continues enough heat is removed and the air is colder and colder. If the system starts with cooler air, then it gets colder faster.

 

[ScottyBoy]

Would not the engine overheat if that were the case?

Maybe. Depends on several other factors though, like ambient temperatures, length of drives/trips, if it's driven on the highway or on slow stop and go traffic.
When my fan clutch failed (or started to fail) I noticed increased temps but only when sitting still. If my truck was moving more than 30mph, it was cooling satisfactorily. But the biggest symptom was te AC was blowing a LOT warmer than normal.
Now I'm nor saying the fan clutch is definitely the cause of the issue, but it's sure worth a check to try and pinpoint the actual cause.

 

[ScottyBoy]

Also, I thought I should add this tidbit of info....
With rear air, even if nobody is sitting in the rear, run the rear air on high if you want maximum output from the front vents. I thought I was imagining it at first, and I still am not completely sure why, but if the rear AC is off, the air coming out of the front vents is a bit warmer. If the rear AC is running on high, the temperature of the air coming out of the front vents gets noticeably colder. Same thing happens in my wife's Chevy Traverse, the air is colder when the rear AC is running.
Those of you with rear AC, try this and tell me if you don't notice the air is warmer if the rear AC is not running, and gets cooler with the rear AC on. And I'm not talking about the entire vehicle getting cooler, we know that will happen when you run the rear air. I'm talking about the physical dash vents, the air blowing from the FRONT vents is noticeably colder when the rear AC is running.