Engine fan won't shut off 99 379 w/ a 60 series

Any ideas would be helpful. No codes, and I have already checked the obvious...i.e., oil/coolant/and intake temperature sensors, high pressure A/C switch, replaced under dash relay, I have read all posts on this forum related to this, and I am pulling my hair out at this point.

 

Bad clutch on the fan sound like if you replaced everything else.

 

Rebuildable I believe

 

Find your fan clutch solenoid, usually on driver side firewall. With air tanks full, key on, engine off disconnect air line going towards clutch you should have air coming out of it. If you do then the clutch itself is stuck. If no air coming out check 2 wire connector on solenoid for 12v+key power on one wire and ground supplied by ECM on other wire. Having both opens your solenoid and allows air to go to fan clutch. Disruption of signals in either of these wires will cause the fan to stay on. On a Detroit it is more than likely the wire from the ECM to the solenoid. It usually breaks close to the connector on the ECM. It is the rear (right) connector on ECM.

 

You got plenty of freon?

 

Good advise ^^^

 

Negative, brand new horton clutch, functioning correctly. My problem is not in the clutch, fan , solenoid, relay, or manual switch.

 

Engine fan light is on, and looking at I/O parameters and dianostic gauges with DDDL software, I cannot see any reason the ecm would be asking it to turn on.

 

If it's a 99 it shouldn't be ECM controlled. The fan clutch solenoid is either going to be normally open or normally closed. Depending on that, the switches for coolant temp, A/C pressure and manual fan switch will be the opposite.

If it's got a Horton coolant temp switch you should double check it. I had to replace mine last year and got a bad one out of the box...apparently there was a bad production run of new switches.