A/C wiring issue

[TJBrown]

ok folks, i have decided to start getting everything ready for the A/C on my 85 SWB truck. Only thing i have left to get it the new hoses which are on order. Compressor, Dryer, Brackets, Hoses, and Condenser were missing when i got the truck.

Here is the issue i am having. I wanted to make sure all the wiring was sound before i bring it to the shop to get it charged. I turned on the AC at the control panel and looked for power at the Low Pressure switch which i have nothing. Does anyone have any input into were i need to go from here on testing?

Thanks in advance