Hoping someone is really familiar with this setup.

I've got the manual, and I thought I understood what was what, but I think not now.

This is a retrofit to another vehicle with no AC. Donor vehicle had AC. I was missing the fan half of the wiring, so I had to make that up.

Secondary fan was easy to wire, hooked relay up to a one wire switch in the head, and the switch side of the relay is getting it's power from the wire that goes to the fuse panel for the fans originally. This fan works if I jump the temp switch wire to ground. Perfect.

The primary fan I'm having problems understanding what it should be doing, and at what time.

I know there is an AC pressure switch, as well as the ECM commanded temp turn-on/off.

The primary fan I didn't monkey with the wiring from stock...just plugged the connector into the relay as it was originally. However, checking voltage at the primary fan relay on the switch side (same wire that feeds the secondary fan relay switch) I don't have any voltage. If I check voltage at the AC pressure switch connector, there is voltage there. If I jumper that connector, I get voltage to the relay switch. (I really don't want to re-loom the wiring yet again lol)

If I jumper the ECM temperature sender wires, while the switch side of the relay is seeing power, nothing happens. My understanding of this circuit is that if I jumper the two ECM temp wires, the ECM will interpret that as being a hot engine condition, and with the switch side of the relay seeing power, when the ECM grounds the other relay switch wire, it SHOULD turn on the fan.

Since the ECM can control the primary fan without the AC being on, I don't understand what the problem is with the AC pressure switch connector. The switch side of the relay should ALWAYS have power, but the AC pressure switch or the ECM should be able to ground the other side of the relay switch regardless of engine temp...so why won't the fan work? Am I missing something or have I interpreted the wiring wrong?

Thanks for any info!