My Fiero is different, and I cannot read wiring schematics, but I believe that both the AC controls and the fan switch hoth pick the relay, and that the fan connects from there.
On my Fiero, the wires to/from the relay go into a harness at the front bulkhead, then run under the left headlight assembly and over to the fan.
I have a brand new fan motor, somewhere. I'm tempted to test the wiring on it.
If the relay does not pic, the problem is not the fan motor. While the ignition is ON, you can short the pin on the fan switch to ground, which should cause the relay to pick.
I suspect the relay is the problem. Possibly bad ground.