I have a dual fan setup on my 91 Z28. The second fan is not coming on (passenger side).

I have tested both fan relays and both fan motors, which are fine and working properly.

I feared it was the sensor in the block that wasn't working properly, so I tried installing a manual fan switch (as a test) to ground the green and white wire going to the passenger fan's relay. It is grounding the wire, yet the fan won't move. I tried it on the primary fan (drivers side) and it worked fine. Because of this, I tested the fan motors by swapping the primary fans wire harness onto the second fan. And then tried swapping the relays.

I think my problem is that the second fan (passenger side) is not getting power through the wire harness. I've checked the fusible links and fuses and all are good.

I am a real novice when it comes to electrical wiring and using a voltometer. What should my next step be?

i can't recall completely, but is that the one that should come on when you kick on the a/c? have you checked that by turning on your a/c to see if it comes on? if it doesn't then it might be because of a bad pressure switch in the a/c line. that's the one that runs down by your pass fender right above the frame - a little 2-wire switch in the a/c line. disconnect that and jump the connector. i don't know for sure if that'll help, but maybe...

KAM