You can take plug off low pressure switch and ground blue with white tracer to fender of truck and compressor will kick on is the ac cycling switch the one with little copper tube that goes into line

 

With this being a closed system and you pulling down the low side, the high side will have been done at the same time. The biggest thing is to draw the system down to 29.9 inches/mercury of vacuum for at least 15 minutes(I prefer for at least 30 minutes). This causes any moisture in the system to be drawn out.

The pressures you gave, were they when you jumped the low pressure switch? This sounds more like an electrical issue than a freon/mechanical issue.

HTH

 

sounds like you just diagnosed the problem - bad cycling switch.

Sent from my Paranoid Android HD2 using Tapatalk 2.

 

Vacuum on either high or low side does not matter. The system is open to both side when not running.

Maybe your Max A/C switch inside the truck in bad...not feeding power to the compressor?

 

Well fixed the problem you know how it is when you do everything but look behind the dash thank you for mentioning maybe fan switch could not be sending power problem solve black wire with red tracer was unplugged off back off ac control

 

Is the a/c wire still hooked up in the back in the heater/ac controls in the cab? It's easy to miss because it is just a single wire and not part of the main wire harness that plugs into the back.

 

Oops, sorry Doug. I wasn't being smart with you. I didn't realize this thread went on to two pages.

Totally missed that!