I have bought a 1999 Blazer 4.3 v6 4x4.
The gentleman I bought it from just put a whole new A/C system in but didnt have enough freon to fill it.. so I took it to my mechanic because we couldnt get the clutch to spin .. he filled it and then it still didnt work .. he said the a/c relay needs to be ground..??? What is he talking about..??How do we do that?? Trying to keep from paying an arm and a leg to him. Please Help anyone?

 

The ground for the compressor clutch relay is provided by the PCM which uses input from the cycling (low pressure) switch located in the filter/dryer on the passenger side of the engine compartment at the firewall as well as the high pressure switch which is located in the back of the compressor. The low pressure switch opens up when the pressure is too low to protect the system and the high pressure switch opens up when the pressure is too high, also to protect the system. If either of these sensors is open, the compressor will not engage.