wiring compressors/pressure switch/relays...

Edited: 10/16/2007 5:26:43 PM by 92yota

ok, i need to hook up two viair 380's, a square D pressure switch, and two 30 amp relays. I will be going by the picture below, which i understand. but i have heard that it is better to wire the ground side of the compressors and pressure switch into the relays because it makes them last longer. this sounds simple, but i keep confusing myself. do i need to switch the power wires in the diagram with the ground wires to go through the relays, and just run the power wires straight to the battery? i don't know

Edited: 10/16/2007 4:27:36 PM by slammedtoys

How would you control the relay then? And what would keep it from running when the car is off? Or would it even run at all because there is no power to the relay to turn it on?

not sure about the advantage to it but it can be done with the ground wire through the relay.
alex- the relay is still wired to the ignition, when there is power from the ignition it just completes the ground circuit going through the relay.

so i need to run the ground wires from the compressors into the 87 of the relays, then from the 30 of the relays to the fuses, then to the negative battery terminal? and run the wire from the ignition to the pressure switch, then to the 85 of the relays? then run the power wires for the compressors straight to the positive battery terminal? what do i do with the 86 of the relays? is any of this right?

Edited: 10/17/2007 5:02:27 PM by layedoutb2k

i would still place the fuse on the positive wire from the battery. i dont think you necesarily have to run the ground to the battery, you can run it to the frame as long as your frame is grounded good. you would still wire the relay the same so that the power from pressure switch goes to the 86 and 85 goes to the ground.

ive never actually wired compresors before because i always run yorks so i could be mistaken. but i do have a vast knowledge from making wiring harnesses from scratch.

Edited: 10/17/2007 9:30:29 PM by 92yota

thanks for the help