a/c switch(one in the steel line by alt.)

[buickturbot]

i think it's the high pressure switch.does anyone know if you have to use it?i'm putting an aftermarket set-up in and it doesn't say anything about it.my factory harness is melted.wires to the switch are no good.has anyone wired it up with an aftermarket set-up?or know where to get a wiring diagram with it hooked up?thanks