'01 T800 Electrical Mystery

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by ecaltd, Oct 4, 2020.

  1. ecaltd

    ecaltd Bobtail Member

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    Oct 4, 2020
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    Here's one that's got me absolutely stumped... Customer has an '01 T800, R/R Brake light won't come on.

    The details...

    L/R lights all work properly stop/turn/running/reverse...
    R/R lights all work as above except the brake function... lamp is good as the turn works.

    Tried new turn signal switch and it meters out as showing voltage to the R/R lamp wire on the connector with bakes applied.

    At the junction box on the back of the frame it shows blinking voltage on the green when turn signal is operating but nothing with brakes applied, again new LED lamps, left side works 100%, right side everything except the brake function, grounds are star grounded to the frame and carried through the harness.

    Any ideas ????

    Thanks,
    gb
     
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  3. spsauerland

    spsauerland Road Train Member

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  4. ecaltd

    ecaltd Bobtail Member

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    Oct 4, 2020
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    874886
     
  5. spsauerland

    spsauerland Road Train Member

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    Sorry, ECAT was down over weekend and yesterday. VIN comes as 2000 W900. Here is diagram for it.
     

    Attached Files:

    BoxCarKidd Thanks this.
  6. BoxCarKidd

    BoxCarKidd Road Train Member

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    It is hard for me to see on my screen but I do not see control modules. Looks pretty old school strait forward.
    I would ditch the meter and use a sealed beam head light or at least a tail light that draws a few amps. How do they work with the previous tests you did.
    Do not remember the particulars but some of those turn switches were wired different. Had to move some wires are in them it get the new one to work. Switch for a Pet put in Ford type thing. The switches looked the same.
     
    spsauerland Thanks this.
  7. TechPL

    TechPL Bobtail Member

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    is there 1 or 2 wires that enters turn signal switch from the brake switch? Since you changed turn signal switch, I would say wire between these two.

    But hey, it happened to me in the past, new parts defect. 4 times in a row, at least I was at a Dealer.
     
  8. BoxCarKidd

    BoxCarKidd Road Train Member

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    Two brake switches.
     
  9. TechPL

    TechPL Bobtail Member

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    One for each side, possible. Would be great actually, because his problem is before the turn signal switch
     
  10. BoxCarKidd

    BoxCarKidd Road Train Member

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    But I do not thank it works that way. One switch is on the primary and the other on the secondary. All brake lights should come on with the foot or hand valve.
     
  11. TechPL

    TechPL Bobtail Member

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    Deplug connector on turn signal switch, depress brake pedal, look for 12V in the connector. Now on the turn signal switch, check continuity from the entry pin and on both left and right turn/brake pins. If you have no continuity for right side, unfortunately the turn signal switch is defect from manufacturer
     
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