Jacob's brake

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Brookshire36, Jun 23, 2022.

  1. Brookshire36

    Brookshire36 Bobtail Member

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    Apr 28, 2020
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    Driving on a unpaved rough road rhis morning, Jacob's brake working fine, made it to pavement drove about 1mile let off pedal and my Jacob's brake wasn't working hasn't worked all day, my motor is a cat c12, and the wires coming from Jacob's brake switch are still running to block, how does it get its power through relay, circuit breaker, I kinda tested the switch on dash and I really don't know if there supposed to light up tester if not working but nothing lit up any help be appreciated thanks
     
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  3. North Pole Nightmare

    North Pole Nightmare Light Load Member

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    We had an old KW,on rough roads a lot.Once in a while you had to put your toe under the throttle pedal and lift it a little,Jake would come on then.
     
  4. Brookshire36

    Brookshire36 Bobtail Member

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    Apr 28, 2020
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    I thought about that also and tried it still didn't work, even tried pulling up on clutch pedal
     
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  5. Dave1837

    Dave1837 Road Train Member

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    Check the clutch switch, just drove a 9200i international with a C13 that did the same thing. There's 2 screws that hold the switch in and one hole is beveled so you can adjust the position of it. Hit a bump and it knocked it off it's position
     
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  6. M22 rockcrusher

    M22 rockcrusher Light Load Member

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  7. lester

    lester Road Train Member

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    Is your cruise control working?
     
  8. Brookshire36

    Brookshire36 Bobtail Member

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    Apr 28, 2020
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    Nope, the one other thing is that it supposed to have a on and off switch, and another switch for low med and high, they removed the on and off switch awhile back so somehow they got power just going to the low med high switch and somehow bypassed med and jsut have low and high
     
  9. blairandgretchen

    blairandgretchen Road Train Member

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    Jacobs Vehicle System
     
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  10. Brookshire36

    Brookshire36 Bobtail Member

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    Apr 28, 2020
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    The one thing is I have no on and off switch somehow bypassed it and all I have is off low and high on the one switch , traced those 3 wires and there all going into the block, so was thinking it has to have a power wire somewhere
     
  11. Milr72

    Milr72 Medium Load Member

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    Oh come on! It's a Jake Brake! :)
     
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