I have an '85 TPI camaro with a single e-fan. I know everyone says that the single fan is controlled by a mechanical temp switch in the passenger side head. I have no such switch, or any wiring to that switch.

From everything I can see, the only wiring that goes to the fan relay is the green with white stripe (ECM), the brown with white stripe (fuse), the orange (Batt), and the black w/ red stripe that goes tot he fan.

Now for whatever reason, when i upgraded to the '89 ecm, my fan no longer turns on when it is supposed to. I know my ecm knows what temp it is since I have datalogged, and I know that my fan works since I have jumped it. The relay has already been replaced, and continuity has been verified on the ecm wire (green and white) and fuse wire. Is the a/c pressure switch wired differently than in '85? In order to get the fan to work properly when I removed the a/c I had to connect the blue and back pressure switch wires.

In the prom there are options for fan turn on temps for a/c on or off, but none seem to do anything. What am I missing?