I've done a few searches and found threads that started off with the same problem, but got off topic, or ended up with band-aid fixes.

I'm working on an '87 IROC 350 with dual fans.

Neither fan will turn on on it's own and the temp gauge is showing 240ish. Neither fan comes on when I turn the A/C on. I can make the secondary fan come on by jumping the relay, so I know the fuse is good and the fan works.

I've replaced the fan switch. I've pulled the fan switch wire off and grounded it with the key on and the primary fan comes on, so I know the fuse, relay, and fan are all good.

What next?

 

If your sure the relays are good, the next place to check is the control for the circuit. In your case the PCM, or the wire going to it.

 

That might explain the secondary fan, but if I can disconnect the wire from the fan switch and ground it out to make the primary fan come on, what would that have to do with the ECM?

 

As far as the secondary fan goes, how would I go about further diagnosing it?

 

Anybody?

 

Well, you said the secondary fan came on by jumping the relay, so obviously that fans relay is bad. For the ECM controlled fan, you said you grounded the wire and the fan came on. So, whatever commands the fan on when its plugged back into the circuit is malfunctioning, rather PCM or the wire going to it.