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1994 FLD 120 12.7 Cruise control

Discussion in 'Freightliner Forum' started by Gibby316, Jul 10, 2025.

  1. Jul 10, 2025 #1
    Gibby316

    Gibby316 Bobtail Member

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    Jul 10, 2025
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    I have a 1994 FLD120 with a 12.7. The cruise is kinda funky on it. I turn the switch to on and the other switch doesn't do anything. If I flip it down to decelerat then really fast to accelerate the rpms will start climbing until I let off the swith then falls back to idle. Will never set. Any help appreciated.
     
    Gibby316, Jul 10, 2025
    Gibby316, Jul 10, 2025
    #1
    Rideandrepair Thanks this.
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  3. Jul 15, 2025 #2
    Rideandrepair

    Rideandrepair Road Train Member

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    Start be replacing switches.
     
    Rideandrepair, Jul 15, 2025
    Rideandrepair, Jul 15, 2025
    #2
    Gibby316 Thanks this.
  4. Nov 24, 2025 #3
    Gibby316

    Gibby316 Bobtail Member

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    New switch made no difference. Could it be in the ECM?
     
    Gibby316, Nov 24, 2025
    Gibby316, Nov 24, 2025
    #3
    Rideandrepair Thanks this.
  5. Nov 25, 2025 #4
    Inderjit

    Inderjit Heavy Load Member

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    The cruise control does not work? Or setting the fast idle with the cruise control switches does not work? Or both?
     
    Inderjit, Nov 25, 2025
    Inderjit, Nov 25, 2025
    #4
    Rideandrepair Thanks this.
  7. Nov 25, 2025 #5
    Rideandrepair

    Rideandrepair Road Train Member

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    My Trucks cruise quit once, along with the speedomete/odometer. Fast idle still worked. I replaced the speed sensor, no luck. I jumped the clutch safety switch, that wasn’t it, replaced the usual, both dash switches, even the brake air pressure switch. About a year later, I accidentally found a second speed sensor on the transmission. That was the problem. Speedometer and cruise started working. Odometer was stuck, never worked again.
     
    Rideandrepair, Nov 25, 2025
    Rideandrepair, Nov 25, 2025
    #5
  8. Nov 25, 2025 #6
    Rideandrepair

    Rideandrepair Road Train Member

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    ECMs get blamed for everything. They rarely malfunction. I guess anything’s possible. I wouldn’t jump ahead that far yet, before ruling out everything I mentioned and the wiring. More than likely it something simple and inexpensive. Unless you turn it over to the wrong Shop.
     
    Rideandrepair, Nov 25, 2025
    Rideandrepair, Nov 25, 2025
    #6
    Gibby316 Thanks this.
  9. Nov 27, 2025 #7
    Gibby316

    Gibby316 Bobtail Member

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    Jul 10, 2025
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    So it doesn't work for high idle or to cruise down the road. Ith it on i can flip it down then back up and it will accelerate but as soon as I let off it it just falls back to idle. I wouldn't think it would be the speed sensor since it won't high idle but maybe it is.
     
    Gibby316, Nov 27, 2025
    Gibby316, Nov 27, 2025
    #7
  10. Dec 5, 2025 #8
    Rideandrepair

    Rideandrepair Road Train Member

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    Have you checked the clutch safety switch?
     
    Rideandrepair, Dec 5, 2025
    Rideandrepair, Dec 5, 2025
    #8
  11. Dec 6, 2025 #9
    Gibby316

    Gibby316 Bobtail Member

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    Jul 10, 2025
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    Yeah I have looked at about everything. Trying not to throw parts at it so I was just hoping someone else has ran into this before.
     
    Gibby316, Dec 6, 2025
    Gibby316, Dec 6, 2025
    #9
    Rideandrepair Thanks this.
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