Need a conformation so I don't break something. Not too whippy with electrical issues. My fans will not come on unless I manually ground them. It appears that I am not receiving a signal from my thermal switch or the ecu is not function properly when the thermal switch activates. I have checked to be sure all of the relays are good and gone back to the ECU pin on the ground side of the circuit (white and blue wire). I have power everywhere I should have power at the relays and if I ground the black and yellow wire the fans work. Also when I ground the pin from the ECU (white and blue) and the fans come on. It looks to me like my problem is not on that side of the circuit. So here is my question. If I ground the wire from the thermal switch (black and red) should that serve as a test to see if the circuit is sending a single to the ECU to ground the white and blue wire? I read how to test the thermal switch, but before I go through pulling it and doing all that I want to know if I can test the wiring to it by grounding it?

 

Yes, you can ground the wire going to the connector and it should turn the fans on.

 

Thanks for the reply. It looked that way but I did not want to risk my ecu being damaged.