1990 T800 No Tractor Brake Lights

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by 1990T800NC, Aug 1, 2021.

  1. 1990T800NC

    1990T800NC Bobtail Member

    1
    0
    Aug 1, 2021
    0
    1990 T800
    No tractor brake lights, trailer brake lights work
    Turn signals work
    Running lights work

    I took the middle dash panel off and I have one large pressure switch with 2 red wires. Power on on side until I hit brake then power to other side. So that brake switch is working. There is 2 other pressure switches back there which appear to be for low air and then something else. I can not for the life of me find the issue. I’ve checked all fuses and nothing. I can apply 12v to rear taillights directly and get brake lights so the bulbs are good. Is there another pressure switch somewhere? Or where is the location for the converter box for the rear light wiring.
     
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  3. Inderjit

    Inderjit Light Load Member

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    325
    Sep 17, 2017
    0
    See if you have brake light power going into the signal switch.
    If yes then the signal switch is the problem. You could try some
    contact cleaner before replacing it.
     
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