aftermarket under dash ac system question

[386kustoms]

hey guys i had purchased a aftermarket under dash ac system a long time a go and i want to install it in my 70 c10. first off there are no decals so i do not have any clue what system it is but it is a old one prob from the 60s

the system has 2 wires coming from the back of the underdash unit 1 red wire with a fuse on it so i know that goes to 12v power.

the other wire is a blue one definitly not the ground cause when i ground the unit and hook up the 12v it turns on. i would assume the that blue wire goes to the compressor but when i hook it up to the compressor voltage drops to 0 for the blue wire

with nothing hooked up to the blue wire but the unit turned on the voltage on the blue wire reads about 6 volts when on high blow 7 volts on med and 8 volts on low. where does this wire suposed to hook to?

also if i direct 12 v to the compressor and ground it the clutch does kick on. any input would be appreciated greatly and thanx

[386kustoms]

i also want to include that i am doing everything on a bench so there is no freon in the unit im just wondering since there is no preasure in the system would that cause it to drop to 0 volts when i try to hook the compressor up