Well crap... Finally got around to pulling some charge out got it down to about 325/45. As soon as the trucks comes down on idle compressor shuts off.wtf man?

 

First of all, you shouldn't do that with R134a unless you released it as liquid. An analogy is to compare it to oil and vinegar. When it is a liquid, it is mixed, but when you let it out as a gas, you are letting out the vinegar, and it will not cool properly. You can let R12 out as a gas, it does not separate into components. The only truly correct way is to remove all of the 134a, pull a good vacuum, and weigh-in the correct amount.

Secondly, are you using proper procedure when you put your gauges on, or add gas to the truck? This means you should first put on the suction hose, and crack open both the high and low side valves on your manifold set, purging the hoses and manifold of air. To add gas, put the refrigerant hose on the can, turn the can upside-down, and crack the hose fitting at the manifold until you see freezing liquid coming out. Failure to follow these procedures will add a couple few cubic inches of air each time you hook up, and air in the system artificially raises the head pressure. It does not always make the high-side gauge wander, bounce, or vibrate, as others have stated. I have "repaired" several car A/Cs by just vacuuming and recharging. If you already knew all of this, maybe someone else learned something.

Thirdly, what are the pressures at the moment the clutch disengages?

 

That's the thing it doesn't matter what pressure u are at. As soon a you let off the gas no more compressor. Period.

 

I'm not a a/c mechanic or anything but my escalade was doing the same thing. A buddy of mine told me to clean out the throttle body. So i did and that worked for my Escalde it was full of gunk it was reducing the rpm idle from 500 to 300 so the a/c compressor wasn't kicking on.

 

What is your idle RPM? These trucks will shut the a/c compressor off as a stall-saver if the RPMs dip down too low. I had that problem with my 01 for awhile until I got it to idle smoothly and at a good RPM. Every time I'd come to a stop the RPMs would dip down to about 400 then jump around a bit till it stabilized at 700. Whenever the RPMs dipped the compressor would shut off.

 

Great info from the last two posts.

 

I'm throwing a trottle body code.. And my Idle does bounce around when I come to a stop, but stablilizes at 850. I hope it's the throttle body because I have a replacement going on with my new heads.

 

Correction idle doesn't bounce around.