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Brake Lights Not Working

Discussion in 'Early CJ5 and CJ6 Tech' started by GeorgeL, May 22, 2016.

  1. May 22, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    Brake lights not working.
    Im tracing the wires from the llghts to a juction box and the wires have changed colour within the 6 inches of connecting to the box!
    The wires in the juction box were either loose or broke.
    I have no idea how this is wired up.
    From there, I followed the wiring along to the brake switch where I found a broked wire.
    I stripped the rubber protective cover back to reveal the other end of the wire which is a different colour!
    Looking over the jeep, who ever rebuilt this must have used any colour wires that was handy.
    Not being a techie and knowing nothing about electrics, Ive thought of a bypass.
    Keep me right on this please.
    Assuming the terminals on the brake switch are live when the brake pedal is applied, I was going to attach a wire to both of them and connect each wire to each brake light.
    Would I then need a ground wire fitted to each light?
    Would this work or do I need an Auto Electrician?
    Sorry my photos to big to upload.
    Any help appreciated
     
  2. May 22, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    Maybe should mention its a 24 volt jeep if it matters.
     
  3. May 22, 2016
    Alan F

    Alan F Sponsor Sponsor

    SE TX
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    Do you have turn signals? If so, your idea won't work.

    If you have power to the brake light switch, then the pressure of the brakes opens the circuit to the lights. I'd check for power there first. If you have it, then jumper the two terminals. If you don't have brake lights after that, the problem is likely in the turn signal switch where it splits the circuit before going to the rear.
     
  4. May 22, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    All the rest of the lights work.
    That includes the indicators.
     
  5. May 22, 2016
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    brake light switch or air in line causing the brake switch to not have enough pressure to close the circuit?
     
  6. May 22, 2016
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    The military maintance manuals and parts lists are excellent, and available. Basic necessity, IMHO.

    IIRC, the original military harness has number tags all over it to ID each wire.

    If it has indicators, in the usual US system the brake light filament is also the turn filament, so the brake light circuit will run through the indicator control on the steering column.

    My early M38A1 does not have signals so I'm not totally sure the military does it this way. It is also possible yours is wired to the European convention, with a separate amber turn bulb independent of the brake bulb.
     
  7. May 22, 2016
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
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    I added turn signals to my M37 using the correct conversion components so yes Pete the way you described is the way it should be for the U. S., but like you mentioned maybe his isn't wired that way.
     
  8. May 23, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    My documents show it was an export to Switzerland so it would be a european spec jeep.
    Also the turn signals are seperate from the brake and night/side lights.
     
  9. May 23, 2016
    uncamonkey

    uncamonkey Member

    Greeley CO
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    So it is a typical three filament system. Still, either the brake switch is bad or some wireing is. First thing to do is use a wire to connect the two wires to the switch. If the lights come on, It's the switch. If not, it is in a wire. Broken wire somewhere or no power to the switch.
    I'll refrain from most of the Lucas jokes except the one about needing your lighter after you walk around to the front of your car to see if your headlights are on.
     
  10. May 23, 2016
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    And I won't even mention how Lucas holds the original patent on short circuits.
     
  11. May 23, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    I hope Lucas doesn't sponser this site !
    Uncamonkey
    I tried two bits of wire attached to a bulb to the brake switch, no light.
    Changed the bulb to be sure, still no light.
     
  12. May 23, 2016
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Bad grounds in tail lights are frequent. Check that each bulb base and it's socket are clean, too.

    But if both are out, it suggests a break in the hot wire someplace.
     
  13. May 23, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    Hi Pete.
    I suspect the wiring, it appears to be a real mix and match.
    Two rallies Ive missed because of these problems.
    Working plays havoc with your jeep time!
    Could this jeep have been built under licence by.............................Lucas!
     
  14. May 23, 2016
    Twin2

    Twin2 wasn't me Sponsor 2019 Sponsor

    Virginia Beach, VA
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    just to add to confusion . does your jeep have this
    [​IMG]
     
  15. May 23, 2016
    uncamonkey

    uncamonkey Member

    Greeley CO
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    It sounds like you have no power to the switch so it could be a bad wire or connection on the dash side of the wiring?
    I reread what I typed last night and you should connect the two wires that go to the switch together and see what happens. If nothing, it's a bad wire. At least over here on this side of the pond there is always one of the wires to the switch that has power to it so the brake lights work even if the ignition is off.

    Send me a plane ticket and we could have that thing in ducky shape in half a day. You may need to supply me with funds to support the beer for John fund.
    My family came here from England some time like 1783. I think I speak some form of English.

    No jokes about Lucas wipers only working when it isn't raining from here. I own no bottle of Lucas magic wire smoke. Bosch wiring can be fun enough.
     
  16. May 23, 2016
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Are you kidding? Lucas actually invented the intermittant wiper.

    Maybe his Jeep caught something from a British vehicle.



    Lucas smoke.jpg
     
    69Willys likes this.
  17. May 23, 2016
    mortten

    mortten I can’t put my finger on it

    Peninsula, Ohio
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    Prince of Darkness. I had a brake switch once that showed continuity across the terminals when activated but wouldn't light the bulbs. Turned out it the connection inside the switch wasn't good enough to allow sufficient current through. New switch fixed it.
     
  18. May 24, 2016
    uncamonkey

    uncamonkey Member

    Greeley CO
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    At least GeorgrL seems to have a sense of humor and we should refrain from telling him that they drive on the wrong side of the road.
    I actually know a a guy that still has a set of them old British sockets. Wentworh or Whitworth or whatever. We would probably have to chase the spiders out of that drawer in his tool chest. I give him a break, his favorite bike is a Norton.
     
  19. May 24, 2016
    GeorgeL

    GeorgeL Member

    Washington U.K.
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    Listen up you people from the colonies.
    We drive on the correct side of the road.
    If my jeep caught something from a british vehicle it would be working!
    Uncamonkey, you family went to America on a prison ship.
    Love the Lucas jar!
    Harley Davidson bought out Armstrong bikes, a major BRITISH suppier of motor bikes to NATO and other friendly countries.
    Quality counts.
    Now can anyone think of an other way to get the brake lights working, maybe bypass the brake switch?
    Im clutching at straws here before I get an expensive expert to look at it.
    You can raz me as much as you want I can take it!
     
  20. May 24, 2016
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Okay, don't get your knickers in a twist. Do we know yet if it's the switch or the wiring? Or something else? Need a shilling for the meter?


    If your jeep has a hydraulic pressure switch that looks something like this, probably on the master cylinder, it only costs a coupla quid. They are available with differing types of connectors.
    [​IMG]


    Alternatively, you could locate a simple universal mechanical switch, and cobble it in some place, hooked to the brake pedal. Some are lever operated, others have an extension spring to pull it "on." Check a motorcycle supplier. Again very cheap.

    [​IMG]

    Even if you have independent orange blinkers, there may be a four-way hazard function, and if so that switch will be involved.

    In either case, trace the wiring, find the place where it changes from "live" to "dead," and fix it. Or, just find a hot wire, tap into it, and run new wires to a new switch and then to the lights, and Bob's Your Uncle. Or your auntie, depending. Will the MOT require the four-ways to function? (Or a better question, do they function now, if you have them?)

    Did you say the this jeep once belonged to the Swiss Navy?
     
    Last edited: May 24, 2016

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