2014 Pete 384 with Paccar MX13 cooling fan always on.

Hey guys. Just as the title says, I have an engine fan that won’t turn off and it does have a new fan clutch and the fan clutch solenoid up on the firewall has been replaced also.

I know the fan clutch isn’t locked up by means of mechanical damage because if you, for example, pull the two air lines out of the fan clutch solenoid and hook them together with a coupler, the fan will shut off but as soon as you put them back in their appropriate place on the solenoid, the fan clutch re-engages, and starts turning the fan again.

One of our outside mechanics that has a much better diagnostic software program than we do somehow thinks the culprit might be the engine temperature sensor that’s located over on the passenger side end of the motor somewhere around the backside of the exhaust manifold but since there’s a lot of stuff in the way to get to it, nobody has yet to dig into that to at least try plugging in the new sensor to see if that might turn the fan off, so do you guys have any other ideas about what might be causing this? The coolant temperature gauge on the dash shows a constant 190-195° degrees.

Also, is that even the right sensor we should be questioning? The reason why I ask that is because like on my old truck which was a 2004 Peterbilt 379 that had the C15 TwinTurbo in it, there was a temperature sensor on top of the engine that went to the coolant temp gauge on the dash but the sensor that the computer used to determine when to turn the fan on was located on the front of the engine somewhere behind the alternator so is there two different sensors on this engine that would work similar to how they did on that other truck? Thanks.