Air conditioning issue

[Zooker]

My truck sat at a shop for a month and the compressor is not kicking on? System was all restored/new parts about 3 years ago and before truck was parked would freeze me out. 1991 gmc 350 p.u. Not sure where to start looking or checking. Any suggestions?

 

[Waterhauler]

Unplug low pressure cutout switch, jumper the two terminals and listen for the compressor to kick on. If it does, it may just be low on Freon or the switch is bad.
I’d check Freon first,, for me that’s usually the problem but I’ve had that switch go bad too. They aren’t that expensive.