Truck Repair: fan clutch electrical, solenoid switch, fan clutch

Question
QUESTION: fan runs all the time, when you shut key off fan free wheels until ecm shuts down. there is only a brief couple of seconds before switch is no longer energized. manual, auto switch does not light up or seem to work. this on a kw900l 06.

ANSWER: Hi scott,
Sounds like a C15, am i right? with the ENGINE OFF unplug the harness at the fan clutch solenoid. run power directly to the solenoid (I usually go to the alternator), this should release the fan..listen for air leaks. check for leaks at the hub and the air line to the hub with soapy water. rotate the fan by hand and see if it is seized. next, start the engine and check if there is power at the solenoid, test with toggle switch in both postions, a/c off and heater not in defrost mode. There should be no power with the switch in manual mode. next, locate the high pressure a/c switch (it should be located near the condensor on the smaller hose..sometimes they have a tag) unplug the switch and check continuity (ohms) through the sensor (never check continuity back through a harness)..the sensor should be closed...it should have continuity. if you have access to OEM software (CAT Electronic Technician...etc..) check what the computer thinks the fan is doing...it should read engauged if the fan is on.

let me know what ya find...

Matt



---------- FOLLOW-UP ----------

QUESTION: Hi Matt, Sorry I forgot to mention it is a Cummins 475 ISX the solenoid switch has 4 wires to it. 2 wires go to part of a 2 piece solenoid the other 2 go to switch where air inlet is red black wire, red wire is energized until you turn off key. I checked hi and low pressure switch they are new and ok. can I check for code without a computer?  

Answer
Hey,
I don't think this would throw a code...it would be nice to see what the ecm status is on the fan thats all. If there was a code you could read it on your dash display....toggle through and see if it shows if the fan is on or not...I'm not sure if cummins displays have this ability or not. Try disconnecting the air line to the hub and charging it with shop air to check for leaks etc...

Sorry I can't be more help, I don't have a lot of experience with newer Kenworths, my experience is mostly peterbilts

Matt