AC compressor shot cycling...
 

AC compressor kicks on an off every couple seconds, when compressor kicks on, pressure goes down to about 16 psi, when it kicks off, it goes to 70 psi, the pressure goes up and down form 16 to 70 as the compressor kicks on and off.
1999 GMC Sierra 1500 5.3L slt
Short Cycling.

I unplugged the connector to the pressure switch and jumped it, it only had 6psi, I charged it to 30 psi, put the plug back on and it works fine, used ac, pro, it took a 20 oz and a 12 oz, the get it to 30 psi, is 30 psi enough? I thought the pressure switch was bad, but it must me OK.

The compressor is running for a long time now and shuts off when I either turn the ac off, or turn the fan off, so it seems it is running fine, old gmc’s never die, they just go faster…lol.

It’s funny because the temperature on the 1999 sierra is 48.4 @ 30psi, and the temperature on the 2011 sierra is 55.6 @ 36 psi.

I don’t know what the pressure should be, according to the can below 50 psi is good.

I have never charged the AC in 23 years, so i would say thats not bad.