2008 Yukon Denali AC fluctuating between Cold and hot

[Joaquin72]

I think it's wild that we're seeing so many posts this week on this exact same symptom across multiple forums and different trucks and generations and even models. They are all low on refrigerant. At least, this is the most common reason for that symptom.

The truck will run a lot cooler with less stress on the system if you get the rear AC working again.

I can work on that.

The question is. What's the capacity if the rear line is capped off?

 

[swathdiver]

I can work on that.

The question is. What's the capacity if the rear line is capped off?

My pickups take 1.6 pounds of refrigerant and 7.1 ounces of PAG oil.

My Suburban/Yukon XL takes 3.0 pounds of refrigerant and 11 ounces of PAG oil.

A Tahoe/Yukon takes 2.5 pounds of refrigerant and 11 ounces of PAG oil.

If 1.6 isn't enough and the lines were capped back aft, then we have to consider that she might take at least 2 pounds and maybe a little more.

If yours were mine I would evacuate the system, pull vacuum on it for an hour and if no leaks detected add 1.6 pounds of refrigerant and then top it off until the gauges read right in relation to the outside temperature. At some point before enough is enough the compressor ought to run all the time with the temp set at 60 and not be cutting out.

FYI: I'll frequently type more than needed to help folks who come along later.

 

[Joaquin72]

Thanks for all the input.

I suspected the compressor was the issue. Due to the fact that the air temp fluctuated when the throttle was used. The rpms were somehow effecting it. Likely something with the clutch.

Had the system professionally evacuated and vacuumed.

Compressor replaced. The old one was the denso original.

It definitely fixed my problem.

 

[donjetman]

The evaparator may be dirty thus causing the clutch to cycle? My 07 Denali didn't come from the factory with a cabin air filter. I added one - Dorman Kit# 259-200.

 

[Joaquin72]

The evaparator may be dirty thus causing the clutch to cycle? My 07 Denali didn't come from the factory with a cabin air filter. I added one - Dorman Kit# 259-200.

Thanks

100 % agree. I'm still going to clean it add the kit. So silly they eliminated the cab filter

 

[j91z28d1]

1.6 seems low to me. 2.0 sounds like a good starting point. but you're really going to need some gauges on it to see what's happening.

my guess is your under charged. you have just enough in there to keep the compressor engaged at idle, but as soon as you start driving the rpms go up and your low side drops below the cut off psi and the clutch turns off.. takes a while to rise back up and click back on.

your buddy should have gauges, put them in, tape them to the windshield and go for a drive. you'll probably see the low side psi drop and click off..

or you'll see the high side spike high and click off. either would be easy to see while driving.

if it's high pressure, maybe check to see if the front ac only trucks take a different o tube.