ISX15 help needed

[Rawze]

(03-07-2022 )4eye4valve Wrote:  ...
fan runs way too much and at very unusual times.
...
It runs more often below 37 degrees.
And nearly works properly when its hotter outside, but still runs too much. Sometimes for hours at a time.

Rick

(cold weather and fan clutch)...
The fan is supposed to run when its freezing outside (to reduce A/C refrigerant pressure) because the A/C is working its arsse off to reduce humidity in the cab, due to the "defrost" / heater on the windshield being active. SO your first complaint is not a complain but you not understanding how the system works. - Personally, I tend to unplug the A/C compressor on my truck in winter times to prevent that crap... but that is just me.


(beaing on when it should not be)...

What needs to happen FIRST is to determine if the ecm/cab controller is "commanding" the fan on.. or if it is on when the computer(s) says it is "off". Until you determine this.. your wasting your time completely trying to determine what it is doing or what may be wrong.

If the fan is on for hours at a time, then look in the ecm (or cab controller) to see what triggered it. Otherwise you will guess until your blue in the face. At the very least, it needs to be determined if the actual fan state matches what the ecm/cab controller actually wants. It is completely pointless to throw parts at it if the thing is being told to be on and it is simply doing what is being requested of it.

Also, if someone has adjusted the "fan on" temperature setting in the engine ecm too low then it will work harder, and more often too.

====

If it is "on" and the ecm/cab controller thinks it is actually "off" .. Then that leads someone towards sticky solenoids, air leaks, or perhaps the common issue of the clutch getting rusted up and hanging up when it rains a lot and the truck sits, etc.