How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask DR.Cummins Your Own Question
Category: Heavy Equipment
Satisfied Customers: 3691
Experience:  16 Years working on Cummins Diesel engines,
Type Your Heavy Equipment Question Here...
DR.Cummins is online now
A new question is answered every 9 seconds

air conditioning off on a isx cummings diesel engine.Terry

Customer Question

what would make the engine fan run constantly even with air conditioning off on a ISX cummings diesel engine.
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  DR.Cummins replied 7 years ago.
hello the fan will run all the time is the switch in the cab to override is in the on position-----Air conditioner sensor or circuit is malfunctioning--------Fan clutch actuator or circuit is malfunctioning---Engine electrical ground is malfunctioning-----Intake manifold temperature or coolant temperature is above the threshold to activate the cooling fan.-------or the fan clutch is locked up or seized hope this helps

Edited by DR.Cummins on 8/18/2010 at 6:53 PM EST
Customer: replied 7 years ago.
It is not any of the above answers already checked those. Could it be in the ecm?
Expert:  DR.Cummins replied 7 years ago.
sure it could be the ecm. The calibration (software version) is out of date or only if someone was in there and changed a setting for the fan. But the ecm controls the fan by receiving inputs from the other components i listed.with out these inputs working correctly the fan will either not come on, go off, or be erratic. look-------The air conditioning pressure switch circuit signals the system that the air conditioner head pressure is high and the engine fan must be engaged. The air conditioning pressure circuit consists of the air conditioning pressure switch signal pin and switch return pin. This circuit is considered “fail safe”, meaning when the circuit is open, the engine fan will be engaged by the ECM.---------The Signature and ISX control system can control the fan clutch activation. The ECM energizes the air valve solenoid which in turn controls the fan clutch..--------
Customer: replied 7 years ago.
all that has been checked any other ideas
Expert:  DR.Cummins replied 7 years ago.
That is all that will do it. Have you had the ecm calibration updated? there is nothing else. Any faults in the ecm or check engine light on?
Customer: replied 7 years ago.
truck was re-geared and the speed calibration was put in through the ecm should not have gotten in the section for cooling.
Expert:  DR.Cummins replied 7 years ago.
i agree should of not but things happen. when your in the ecm changing stuff...... is there a way for you to recheck the settings in the ecm and compare to the oem spec's? i have seen ecm's just forget stuff after changes, or some changes just dissapear. but it is not often.
Customer: replied 7 years ago.
i have checked all. i guess i will need to take to cummins to plug this up to check it out
Expert:  DR.Cummins replied 7 years ago.
that will be the best bet if you have check and verified all components are working.
Customer: replied 7 years ago.
Expert:  DR.Cummins replied 7 years ago.
Thank you Have a great day