2002 GMC Sierra 5.3 AC wont stay on

[morganiser]

The Air goes on in the morning first thing and then after a short while goes off and will not reengage. I have evacuated the freon...replaced the inline filter...filled the freon back up to the required 1.8 lbs and checked for leaks...all is well except for the fact it doesn't work. I jumped the high pressure switch...makes no difference. Any ideas on what to do short of replacing the compressor?

[GM Tech]

What you describe is a very common failure mode- next time it quits cooling when you know it should be on, let engine running, pop hood and look at front of compressor, is it turning? Here is a cut and paste from previous post like yours

Next time it is blowing hot and it should be cool-- stop, pull over, keep engine and a/c running, pop hood, look at front of compressor- is it turning? If not, bump it with a wooden hammer handle. If it engages, starts running, you have an air gap issue, that is too wide.

Does it normally cool when first tried each day, then later on after engine is hot, the a/c quits? This is another big hint- magnetic coil resistance is greater when coil warms- such that it has trouble pulling in a clutch armature when air gap is worn too wide. When cool it can do it, problem always starts happening after coil gets warmed by engine heat.

If all above are true:
most shops would merely replace the compressor- we here recommend removing a shim behind the clutch driver to "narrow" the air gap....simply remove the driver- wiggle it off the splined shaft, look for 1 or 2 shims behind the driver, throw the thickest one over your shoulder and replace the driver- and be cool for the next 100k miles.....

[Cusser]

The Air goes on in the morning first thing and then after a short while goes off and will not reengage. I have evacuated the freon...replaced the inline filter...filled the freon back up to the required 1.8 lbs and checked for leaks...all is well except for the fact it doesn't work. I jumped the high pressure switch...makes no difference. Any ideas on what to do short of replacing the compressor?

Check for electric actuator failure under the dash just right of the center hump. I had this issue on both our 1994 Suburban and 2005 Yukon: Air would start coming out hot from the vents. Turning the engine off, then on would temporarily "fix" this.

At first on the 2005 I just took off the undercover (not easy) and unplugged the harness to the actuator when it was in the "cool" position as I'm in Arizona and needed AC more than heating. Then after a year I ordered an aftermarket actuator using the GM part number on mine as cross reference, ground down (both ends) of a 5.5mm socket to make it shorter (the hump is in the way, thanks GM !!!) and removed the actuator. After bolting in the new actuator, there's a procedure to let computer recognize it, like leaving connected for 10 minutes, then turning on to run position but not starting for 10 minutes, or something similar - look that up on the Internet.

Anyway, that fixed it on the Yukon, cost me about $60; mechanic cost for the 1994 Suburban one was over $300 for parts and labor. Anyway, I've left the undercover off, and now I have a short 5.5mm socket.