OE, OEM or aftermarket WP and Thermostat?


I think the cut out relay provides power to the Fan. As long as the control signal on Pin 1 is powered it should conduct power to the fan.


That relay isnt controlling the fan. It controls the POWER to the fan


The fan itself is controlled on pin 4 of X1797 ..and that signal is a PWM signal.




and I dont think it is coolant 'strength'....


DO NOT jumper any of that.


You should monitor the wire to that relay on pin 1, and also the two heavy red wires on X17278, X17279 and see that they are indeed 12V and stay that way when driving and in the driveway.


Any reason to suspect some of the other temp sensors?? (which the DDE uses to decide when to run the fan...)