Yeah, I'm going to start all over again this weekend. I just cleaned and verified good grounds and still no dice. I will jump the A/C switch as well, and see if and what that triggers.

 

Hopefully I did not overlook this in your posts, but have your tried providing each fan with a 12v power source directly to confirm they are working?

My radiator fan (90k+ miles / ~10yo) was working intermittently and giving me quite the headache. Sometimes the fan would turn, and sometimes it would not. When it was not working, a sharp impact with screwdriver handle & mallet would get it started. I did not have any blown fuses or damaged relays, so I never thought to check this first. A closer inspection of the fan motor after replacement revealed extremely worn brushes and brush springs resulting in unreliable contact.

 

 

 

I'm totally at a loss now. turning on the A/C triggers the radiator fan switch (toggling it with a voltmeter hooked up indicates it is seeing voltage and the circuit is not broken) so both should turn on there, yet if I unplug it and jumper it nothing happens.

Also bypassing the relays with a jumper wire will trigger either of the fans to turn on - so I know my wire harness after the relays is functioning. I have swapped relays with every other relay in the car and verified that they all work. I also pulled every single fuse one by one and looked.

What else should or could I look at?

 

It very well might be the fuse box itself, or the radiator fan motor has seen better days. Try getting a used fuse box on ebay or something.

 

I sure hope not.... I think for the time being until I can figure it out, I will wire a switch so I can bypass the relays and turn them on whenever I need to. With summer approaching I'd rather not overheat.

 

Have you removed the fuse box and inspected it? The manual says when all else fails replace the fuse box(which is why I'm suggesting it seeing as you've pretty much exhausted every other option), and used ones can be found online for ~$30-40.

 

Look at the diagram I posted above.
Check for continuity between chassis ground and the fan switch.
Then bypass the fan switch connector and check for continuity between ground and pin 4 on the fan relay sockets.
Pin 3 on fan relay sockets should always have battery voltage.
If you look down on the relay socket pin 4 is in the middle and 3 on the side closest to the passenger wheel.

 

we narrowed it down to the signal wire on the radiator fan switch wiring. ground is good on it, but the signal wire is broken somewhere between fuse block and radiator end connector. I will be tracing it starting at the radiator end and seeing if and where it is broken.


looking at the diagram, the ECM should be able to over ride the switch and signal fans to turn on, correct?