Cummins Isx fan clutch problem

Make sure the switch is good

 

Fan override switch should be an input to the ECM separate from the fan clutch and solenoid circuit. Like truckmechanic said, check your switch. I think the ECM is looking for a ground at pin (15) of the OEM connector to have the fan off. The override switch allows this path to ground. When you want the fan on and toggle the switch it opens the circuit, ECM no longer gets a ground at that pin and signals the fan to come on. This is how Cummins has it, it is only how they recommend it, KW may do something differently. Hope this helps..

 

Switch mounted in the A/C line from the compressor to the condensor. But sounds more like the dash switch has failed.

 

Those generally require air to release, so either it's not getting air, or it's not holding air. First thing I'd check is to make sure the air isn't just leaking through the back seal, that could indicate a bearing going bad and overheating the seal. If you continue to run it like that, it could go through the radiator. $$$$$.

 

My fan clutch stays on any body know whats going on

 

Any update pn how it got fixed?