2004 GMC 2500HD 6.0L gas engine. I had a clutch burn up on my ac compressor, so I changed it, the dryer, and the orifice tube. I started charging it and everything was working fine the compressor was cycling on and off until the second can and it just quit... (This has been a while back so I don't remember exactly but gauges were reading within normal ranges but still low obviously since it was only the second can). I can bypass the relay and the compressor kicks in and cools but that is the only way. Also, I have tried to jump the low pressure switch but that doesn't do anything. My dimmer switch is going out on the dash (I think) because occasionally the dash lights will go dim or completely out and I have to scroll it down and back up for them to return to normal... Is there a correlation between the two?

your computer controls the activation. there is the pressure switch obviously, but also temp and some other things. so this time of year it may not engage to charge it. you could just wait till a 50 or 60deg day to see for sure. or some of the high end scanners will see inputs and can lock on the compressor.