2000 Freightliner FLD, Cat C12 -- Cruise not working

Discussion in 'Freightliner Forum' started by ichudov, Sep 17, 2020.

  1. ichudov

    ichudov Medium Load Member

    674
    539
    Mar 14, 2012
    Berkeley, IL
    0
    So I have this beautiful and amazing year 2000 Freightliner FLD with a Cat C12 engine. It is the love of my life and an amazing truck overall. Made me so much money since I bought it 6 y ears ago.

    However, the cruise control stopped working and I hate this.

    I have done some investigation and even bought a 4,400 page Freightliner FLD manual PDF file. Here are some facts:

    - Cruise control has the On/Off switch, and also the "Set/Resume/Accel/Decel" switch.
    - The cruise control is not working neither in Park, nor in Drive
    - Cruise control circuitry is supplied by the engine ECM Pin 790 (12V)
    - There is +12V at the input to the On/Off switch, as well as on the input to Set/Resume switch
    - There is no 12v input at the clutch pedal switch, none of the switch's three terminals has live 12v, even though it is supposed to be also connected to Pin 790.
    - The clutch pedal switch is also supposed to be supplied with 12V from Pin 790 of the ECM
    - I tried to jump and connect 12V from cruise on/off switch to the clutch switch. It did NOT help! Still cannot set cruise at idle

    Questions:

    1) Does anyone have schematic and explanation of how exactly cruise control works on my truck and what sensors does it utilize (clutch, brake, park).

    2) Is the brake switch for cruise the same one that turns on the brake light or it is a different switch?

    3) Also does anyone know where the brake switch is located?

    Thanks!!!
     
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  3. ichudov

    ichudov Medium Load Member

    674
    539
    Mar 14, 2012
    Berkeley, IL
    0
    After a lot of angst and suffering, days spent figuring out, it turned out that the culprit was the "brake application pressure switch for cruise control", located on the fuel/oil junction block.
     
    AModelCat and 25(2)+2 Thank this.
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