A/c weird issue

[Tf79]

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?

 

[OR VietVet]

Guess, the system is not full or low pressure switch. What are the pressures when this is happening? Ambient temp when happening?

 

[CraftyCrafts]

Ambient air temperature sensor(s) or maybe the engine temperature sensor

 

[rockola1971]

As OR said....need to know what the ambient temp is outside during a refrigerant pressure test. Need to know that low side pressure when compressor is engaged. The pressure reading when compressor is not engaged is useless. You should be seeing around 45psi or so consistently while compressor is engaged and even higher if you live in high temp areas. The pressures are directly related to the outside air temperature. All readings taken with fan on high, max cooling front and rear A/C.

A proper vac pump down will prove no leaks. I let them sit under vac for hours and then check gauge over atleast an hour period. Most common leaks is the schrader valve cores. Always snug them after hooking up and gauges to the them. Leaking evaporators and the lineset at the rear are also common culprits.

 

[ScottyBoy]

Sounds like a faulty fan clutch. Perfect time to convert to Electric Cooling Fans in my opinion.

 

[rockola1971]

Sounds like a faulty fan clutch. Perfect time to convert to Electric Cooling Fans in my opinion.

Would not the engine overheat if that were the case?

 

[OR VietVet]

Would not the engine overheat if that were the case?

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

 

[rockola1971]

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

Yup. With the minimal info we have I would say OP is either under or over charged.

 

[Tf79]

Guess, the system is not full or low pressure switch. What are the pressures when this is happening? Ambient temp when happening?

Just got the evac and recharge at dealer done. Ambient temp is around 90 when it happens

 

[Tf79]

As OR said....need to know what the ambient temp is outside during a refrigerant pressure test. Need to know that low side pressure when compressor is engaged. The pressure reading when compressor is not engaged is useless. You should be seeing around 45psi or so consistently while compressor is engaged and even higher if you live in high temp areas. The pressures are directly related to the outside air temperature. All readings taken with fan on high, max cooling front and rear A/C.

A proper vac pump down will prove no leaks. I let them sit under vac for hours and then check gauge over atleast an hour period. Most common leaks is the schrader valve cores. Always snug them after hooking up and gauges to the them. Leaking evaporators and the lineset at the rear are also common culprits.

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?

 

[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.

 

[rockola1971]

Is there frost or ice on the evaporator lowside line at the drier? (The bigger line) or is it sweating cold droplets?

 

[Tf79]

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.

Yes. However when it’s sitting in hot air I can hear the condenser cycle on and off immediately as soon as it’s idling and after I turn the air on. In the morning it turns on once and then stays on

 

[Tf79]

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.

I’ll try that today after work

 

[Tf79]

Is there frost or ice on the evaporator lowside line at the drier? (The bigger line) or is it sweating cold droplets?

It sweats a little and when I turn the truck off it pisses. I’ll take a video of it after the drive home from work and post it