Cat C15 MXS Engine Fan Not Coming On Automatically

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by CameronEldridge, May 30, 2023.

  1. CameronEldridge

    CameronEldridge Bobtail Member

    May 30, 2023
    I have a 2012 (316678) KW W900L tri axle dump truck that had the ISX15 from the factory, that engine started getting tired so I had a shop swap a 14:1 C15 MXSS02666 with a 120 pin ECM, 55 injectors, C18 marine cam and 80/1.45a/r billet turbo, come to find out, the shop that did the swap had absolutely no experience with this kind of job like they assured me they did (very long story). Long story short they got the engine installed and hacked up all the wiring behind the dashboard, and from the cab to Ecm. My mechanic and i had to go to there shop and spend a week getting the truck somewhat roadworthy enough to get it to my shop so we could try and finish the job.

    The engine fan... the manual switch on the dash only has 2 wires connected to it with blade terminals and dives into the main harness, no clue where from there, however, that switch operates the engine fan properly, manually. the fan will not turn on at all automatically from coolant temp. or a/c switch. I have checked with a temp gun, and it seems to be accurate, ET and the coolant gauge are accurate. Have taken it all the way to 219 and it does not turn on.

    My mechanic noticed that pin 11 for the fan control was not hooked to anything and ran it to a relay then to the solenoid. You can operate the fan with the switch or Cat ET but it will not come on at 215*-217*?

    We have also changed the fan control type to- On/Off DC, On/Off PWM and None with no luck.
    The fan override switch was also set to none, and we changed it to- J1939 Cab Controller, with no luck.

    I am really starting to lean towards the ECM being bad since it is getting signal that the engine is hot, but not kicking the fan on even though you can kick the fan on with ET. I just want to make sure I have crossed all my T's and dotted all my i's before i purchase a new ECM.

    Thanks for any and all help!
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