I have an '01 1500 with the 5.9. and AC trouble. Works upon cold start, but shuts down in short driving time. System shows propper charge and jumping low pressure switch does not get clutch to engage even though it shows propper voltage. Also, will not engage after turning switch off then back on when it is running. Although, I can get clutch to engage by tapping it with a piece of wood. Not sure if it is clutch, vaccum or lack of patience. Any ideas welcome. Thanks.

 

Had another member with the same problem. Figgered it was the coil for the clutch getting weak/failing. You might be able to find just the coil, but, most places list the whole compressor......

 

Vacuum only controls vents. Nothing with controlling the clutch.