Radiator Coolant Fan Runs All The Time

Ivylog wrote:
The good news is it's not a Sauer Danfoss controller... $$$. I believe your sensors are normally closed so you get 12V to the fan solenoid which slows it down until needed. Looks like the air inlet temp sensor keeps the fan off when cool air is coming into the engine intake so bypassing it should not hurt anything... in fact I'm not even sure why it's needed. The Sauer Danfoss complicated system only senses engine temp which is what you've done in the last diagram.

*At some point (first diagram) they did not feel the need for a air inlet temp sensor. I do not think you need one now but if it's a reasonably price sensor... why not as it may sense the need for more cooling sooner than the engine temp sensor.

I agree, to me the diode does not make sense, why is it there?

I suspect that as a temporary fix I could tie the Yellow and Red wires running into the Air Inlet Fan Temp together (no cutting, I have the weather pack connectors and can make a shut plug).

Any idea where the sensor would be. The red wire goes into a harness at the rear that is about two inches in diameter, I have traced it across the rear of the engine, but then lose it.