wiring compressors/pressure switch/relays

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. 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?

ok, i suck at paint, but this is how to do it.


Click the pic to make it large....

so the ignition goes to the 85's, pressure switch T1 goes to ground, and pressure switch L1 goes to the 86's? is that what you're saying?

yes, exactly!

thankyou for the help. ok, that takes care of the pressure switch. so i need to run the compressor grounds through the relays, and run the compressor power wires straight to the battery, sound right?. but the fuses should still be put on the power wires not the grounds? and does it make any difference running the grounds to the negative side of the battery or running them to the frame?

the frame is fine, as long as you make sure you are grounded to clean metal.

as far as the wiring, you ground the compressosr to the frame, run the power wire off of the compressors to #30 on the relays, number 87 on the relay goes to the positive batt term (thru a fuse of course) and the #85 terminals on the relays go to the switched power wire (should fuse this too) then the L1 on the press switch goes to ground, and the T1 goes to #86 of the relays, just follow the pic exactly!!

earlier you said that L1 goes to 86 and T1 goes to ground?

but i was told that wiring the compressors to the relays through the ground wires (instead of power wires) will make the relays last longer or is easier on them or something. i have heard this from a lot of people, as well as doing the same thing with the pressure switch. does that make any sense, or would it really not matter?

And people think minitruckin' is easy.