Weird, I've been trying to help another member on the board and I'm stumped. His car is a 88 camaro with a 305 tpi and dual fans. His car doesn't kick on the fans at all. We tried everything but nothing works. Fan motors, relay, and are newest thing, the prom. We put the his prom in my 89 Formy 350 tpi and when ever the car runs, the driver's side fan is on even when the engine is cold. Passenger side fan kicks on somewhere between 220 and 230 according to the gauge. Why does this happen? Why does the chip work in my car, weird but works and doesn't work in his? When his fans did kick on, one would at 220ish and the other at 240ish. What happened? Is there a different programming? Is this a phantom programming from "Generous Motors"?

 

I'm surprised that no one has any ideas. Maybe people missed it. So, BUMP!

 

one fan is controlled by the ecm. the other is controlled by either a hard temp switch in the cylinder head (factory, passenger side between 6 and 8 cylinder), or the AC request.

each is controlled by its own relay.

if you've already changed the fan motors, and relays, and prom, and the one fan does turn on, I suspect it's possible the ecm is faulty. the quad driver internal to the ecm could be failed.

you can ground the signal for each fan to verify that the relay and fan and wiring is all intact. I believe the fans have their own fusible links or hard connections directly to the battery. You can make sure you are getting 12 volts there. It's easy to test the ac controlled fan, you can pull the connector off the switch in the cyinder head and ground it.

I would unplug the ecm and probe the connector on the fan wire, and connect that to a ground, to make sure everything up to and including the connector to the ecm was good. that would point to the ecm as suspect.