Where is this located (near to the evaporator would be my first guess)? What does it do? Does it protect the compressor (meaning it won't turn on) when low or no refrigerant is in the system? Or do I have it all wrong?
Wanna make sure everything is in working order before attempting to recharge ac with good ol' r-12. Can anyone clue me in... Thanks

 

If you are talking about the switch that is on or near the large silver canister under your hood, that would be the low pressure cut-out switch, yes. There also is a high pressure cut-out switch that is located in the back of the compressor.

 

Ahh yes... The wiring schematic in my chilton has it labeled as the evaporator control switch. Any how, I jumped the connector to the switch momentarily and the compressor clutch engaged when I switched the AC to "ON" in the cab (as it should). The electrical side of the system seems good to go. Thanks much!!