Trailer brake lights come on with blinker

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by OldeSkool, Mar 5, 2019.

  1. OldeSkool

    OldeSkool Road Train Member

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    So on my 07 Freightliner Century the trailer brake lights come on when i turn on the left blinker. It does not do it if I turn on the right blinker. I checked my electric cable running to the trailer with a test light and sure enough the brake light prong lights up when I turn on the blinker so has to be on the truck right? Any ideas?
     
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  3. OldeSkool

    OldeSkool Road Train Member

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    Also the trailer brake light occasionally stay on after I have let off the pedal for a while. Not sure if that could be connected with it.
     
  4. BoxCarKidd

    BoxCarKidd Road Train Member

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    The first I would most likely blame on the signal switch. Have someone watch the lights while you move the switch handle a little past or before where it stops by itself. If the lights every work correctly it is probably the switch.
    The second I would thank is brake light switch related. There are two of them. Is it possible the plunger under the brake pedal is sticking and holding a little pressure on the system?
    Two different problems at the same time seems odd.
     
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  5. OldeSkool

    OldeSkool Road Train Member

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    Thanks Bud!!! You were right on the blinker switch. I'll check the brake light switch when I get time
     
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  6. Tombstone69

    Tombstone69 Road Train Member

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    Check you're trailer ground, sometimes when the trailer's not grounded well the taillights will blink with the signal lights. You can check it by using a jumper between the trailer and the tractor.
     
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