nws, my apologies for taking this long. Unexpected trip out of the U.S. I'll post these 2 schematics. 1 is original wiring tied into the ecm. 2nd is how I did mine. Since I have a Cummins engine, and am not using the original ac compressor, I used a binary switch in place of the GM high pressure cutout switch. It does the work of both the Hi and Low cutout switches, as my compressor does not have a port for a separate Low cutoff switch. With that in mind you may be able to use the switches that you already have in the factory setup. To determine if you can do that you will need to ohm the Low cutoff switch that is in the back of your compressor. Unplug the wire terminal and Check for continuity across the switch in the compressor. If that switch shows closed (reads continuity) then just wire your 3 switches in series....like I have done with my 2 switches. If that switch is "open", no co tinuity, then you'll need to buy the binary switch and wire 2 switches in series like I have done. Any questions at all, ask away.