I just had my 93 Del Sol overheat and it was the fan not running also. I jumped the thermo switch (no change), I wired the fan direct to 12V and it ran fine, I removed the relay and tested it with a 9V battery and it worked. I checked the fuse and that 12V was at the relay, everything good; but the fan will not run!

What is left? I must be missing something.

 

I've found that wires can break particularly right at a connector. The insulation will hold the wire together making it appear ok but the wire inside is broken. This happened to my thermoswitch for the ECU (the one the ECU uses to sense engine temp). The guy at the Honda dealer was very helpful he gave me new connector parts (the little metal parts that receive the blade connectors in the connector housing). He showed me how to coax the connector housing apart with tiny screwdriver (there is a rubber plug that kind of holds the whole thing together). A few minutes with a crimper and pushing the connector back together and my intermittent CEL was gone and my connector was like new.

In summary, wires do break, check near the connectors where they break most often due to abusive manipulation or vibration.

 

OP -- For clarity, I converted your post in a thread.

 

How did you test the relay with a 9v battery?

 

I clipped an Ohm meter to the power side terminals and took a 9V battery with a power snap connector (I get them for guitar stompboxes) and activated the relay side and you can hear it fire and the resistance goes to 0.

 

Hopefully you don't do the same dumb thing I did and check the sensor next to the front hose (the temerature sensor) instead of the back sensor which is the fan sensor next to the thermostat housing. When I jumped the back one the fan came right on.

The good news is while testing I noticed that the hose to the thermostat was cold. So I will change out the thermostat and have the housing out to change the sensor.

Guess thats why I don't do this for a living.

PS something nice to know this page on Autozone has a explosion of the housing.