No trailer brake lights??

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by CDL CPL, Jan 18, 2020.

  1. CDL CPL

    CDL CPL Light Load Member

    178
    62
    Aug 14, 2017
    Iowa
    0
    We got no trailer brake lights. All other lights function like they should. Checked all fuses. Not sure which is the correct relay under the hood. It's a 2013 Freightliner Cascadia. Does anyone have any suggestions on what to do?
     
  2. Bry

    Bry Light Load Member

    145
    77
    Apr 16, 2013
    0
    Sometimes it is just the plug near the gladhands. Try jiggling it, pushing it in harder, or even using a screwdriver to gently, slightly bend the prongs in the socket. Also adding a little conductive grease could help.
     
  3. Intheoutfeild

    Intheoutfeild Light Load Member

    68
    40
    Dec 15, 2007
    out there
    0
    Get a DC test light or a pig tail tester and check all connection sockets at the pig tail (trailer side) if good then the trailer wiring is bad, look in the light boxes (boxes that hold the marker/turn/brake lights) at the back of the trailer for corroded wires or cut wires, if pig tail is good test the pig tail connection at the tractor and back trace it from there. most times it is the pig tail unless it is is a old trailer.
     
  4. Bakerman

    Bakerman Road Train Member

    4,313
    7,391
    Jan 27, 2013
    Phoenix, AZ
    0
    Just had this problem last weekend. First tried the pigtail, nothing. Then went underneath the trailer where there are two connectors where the wiring crosses over from one side to the other.

    I unplugged those tow connectors then reattached, came out to look at lights and they were back on. Amazing!!
     
    baha Thanks this.
  5. O.Henry

    O.Henry Medium Load Member

    534
    456
    Sep 1, 2012
    San Antonio,TX.
    0
    I had a problem similar to that,and it was a connection behind the cab wall.
     
    baha Thanks this.
  6. xsetra

    xsetra Road Train Member

    3,560
    3,334
    Aug 21, 2011
    0
    Check for power to brake lights.
    Check for power in pigtail.
    Then check connection in the nose junction box, where the pigtail from truck plugs in to trailer.
     
  7. CDL CPL

    CDL CPL Light Load Member

    178
    62
    Aug 14, 2017
    Iowa
    0
    Turned out being the wiring under the trailer in the power box. Guess wire had jiggled itself loose. Now the issue is getting it set in there again to stay without having to open power box, which we will probably end up having to do but when it's warmer outside. Thanks for all the tips!
     
    xsetra Thanks this.
  8. xsetra

    xsetra Road Train Member

    3,560
    3,334
    Aug 21, 2011
    0
    Good to here you... Sorta.... Fixed it.
     
  • Draft saved Draft deleted