PCM cooling fans
#21
#22
You can use a small for all the relay grounds to the same place the PCM is grounded to the chassis. A big wire for the fan to any other chassis location. They all end up at the same place, but there are losses and noise generated in ground wires and you want to keep that away from the ECM. I may be over engineering this, but I like to keep my power and signal circuits separate.
Hope this makes sense. Basicly from my diagram I will reverse my relays on the a/c side only and connect the neg feed from the relays to the 2 pcm wires coming from the pcm.
I hope this makes sense