My brake lights don't...(light, that is)

Discussion in 'Tech/Mech General' started by Bryan, Sep 4, 2009.

  1. Bryan

    Bryan Read Only Funster

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    Hello all you electrically mined people in fun land :thumb:


    The brake lights on my Rv don't light. They used to, but now they don't.

    There are two switches on my brake pedal, one has two wires and the other has three. I think the two wire switch is for the cruise control cancel operation but I may be wrong.

    The three wire switch has one wire which I've been told is to do with the transmission (?) and a permanent live and when I depress the switch the 12v goes down the third wire. So I don't think it is the switch.

    All fuses are fine and the bulbs are fine too.

    I have a tow socket which I think is scotchlocked into the light clusters. A light board on this socket also fails to light it's brake lights.

    If I connect my toad and apply it's brakes, the RV brake lights illuminate also - hence my knowledge that bulbs are okay.

    I had hoped to trace the wire from the brake pedal to the light clusters and to this end I bought a tone generator and wire tracer. I have put the tone generator on the wire that get's 12v from the switch mentioned above (when switch activated) but I can't seem to trace it anywhere - even away from the switch.

    I don't have a chassis manual unfortunately (workhorse 2001)

    Can anyone offer any suggestion?

    (Note: Possibly unrelated but my cruise control also stopped working at about the same time)

    TIA

    Bryan
     
  2. davejen

    davejen Funster

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    Hi, Bryan if I were you I'd check the scotchloks - they're notorious for being crap and not working properly. If you can replace them with proper connectors 1 at a time so you don't get them mixed up. Hopefully this should solve both problems as the c/c won't be getting a signl so won't work.
    Cheers, Dave:thumb:
     
  3. Bryan

    Bryan Read Only Funster

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    Thanks Dave,

    Because my toads brakes activate the RV brake lights, surely that means the scotch locks are okay?

    Also, wouldn't a nasty scotch-lok failing just take out the one light, not bboth + the high level?

    The scotch-loks are in the light clusters...
     
  4. pappajohn

    pappajohn Funster Life Member

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    hi Bryan,

    does the two wire switch work ? power in and out when pressed or possibly earth return from lights through switch to earth.
    easiest way to check....remove both wires from the switch and join together...if they work its the switch, if not its a fuse or wiring fault.

    i would expect the 3 wire switch to be for the cruise and transmission switching (both circuits in one switch) and the 2 wire switch for the brake lights.

    saying that, the yanks have some strange ideas of lights and wiring.
    side lights and tail/brake lights flashing for indicators etc.:Doh:
     
    Last edited: Sep 4, 2009
  5. davejen

    davejen Funster

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    Probably, so look then at the feed from the switch, get someone to press the brake and then see if there is a feed to the lights, if not then you'll have to check the switch again- is the 3rd wire live when switch operated? and where does it go- it may be to the indicators if they have been changed to amber.
    Dave:thumb:
     
  6. Bryan

    Bryan Read Only Funster

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    Am I missing something? Why would a wire from the brake pedal switch go to the indicators ?:Eeek:
     
  7. pappajohn

    pappajohn Funster Life Member

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    i wondered that as well.......then i thought ....Mmm!!! yanky wiring.:Rofl1:
     
  8. davejen

    davejen Funster

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    I'm sure the brake lights and indicators are the same light so I think they are wired through the brakelight switch as pappa says.
    Dave:thumb:
     
  9. haganap

    haganap Funster Life Member

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    Sorry Bryan, But I just can't resist it




    HAVE YOU CHECKED THE FUSES:Rofl1::Rofl1::Rofl1::Rofl1::Doh:



    In fairness though, i think a long trace through the wiring starting at the brake switch would be a good start. Find where you are live to from the begining of the switch and then start tracing through. Tough job me thinks, also a long shot would be if your tow equipment has shorted something.
     
  10. Bryan

    Bryan Read Only Funster

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    Thanks John and Dave for the help...Paul? You can just shutup, alright :Rofl1::Rofl1:


    I have it on good authority that the three wire switch is the brake light doofer...but you make a good point about the indicators of course...Originally the RV when in the states will have been wired for flashing brake/tail lights for the indicators. Altered in the UK and that will be why some of the wires are scotch-lok'd

    I'm leaning towards a dodgy/broken wire rather than the switch. The switch with three wires, when activated, allows 12v through.

    I now think the other switch (2 wire) is a lockout for the gear lever (Won't move out of park unless brake pedal pressed.

    I just wish I had the chassis manual - I'm sure it would help :Doh:
     
  11. Jim

    Jim Ringleader

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    I think haggers is right, its a fuse, you just have to find it:BigGrin:
     
  12. Boo

    Boo Read Only Funster

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    Is it relay assisted? have you checked them?

    Just a thought............good luck :thumb:

    Boo
     
  13. PenelopePitstop

    PenelopePitstop Funster Life Member

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    ..Paul? You can just shutup, alright :Rofl1::Rofl1:


    Hmmmm - think I may just have to publish the photos of you upside down on your driver's seat in Couhe !!!!! :Rofl1:
    I'm dong a good line in blackmail after France!!!!

    He he he!!:Rofl1::Rofl1::Rofl1:
     
  14. Bryan

    Bryan Read Only Funster

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    Right, I've been upside down again...:Doh:

    There are two switches on the brake pedal...One with two wires that activates a solenoid(!) that prevents the gear lever being moved unless the brake pedal is pressed...This works fine.


    The other switch has three wires. 1 x white, 1 x orange and 1 x purple.

    I've been told that the purple wire is something to do with the transmission...

    The orange measures 12v all the time.

    With the ignition off the white measures 0v with the brake off, 12.4v with it pressed.
    With the ignition on the white measures 4.4v with the brake off, 11.6v with it pressed

    Voltage drop aside, this indicates to me that the switch is working (assuming that the orange IS the feed and the white IS going to the brake lights.

    BUT my brake lights never light :cry:


    Does this help anyone to help me? :thumb::cry::thumb:

    Bryan
     
  15. haganap

    haganap Funster Life Member

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    Ok Bryan, I will shut up about ya fuses.

    Ok, You have power out of the switch. Which blows my theory of the solonoid.

    Have you checked power at the lback lights on both side? I know we checked the bulbs but did we check the circuit at the bulb end? if so and there is no short at the tail light holder then somewhere in between your problems surely exist. I have acdcdave staying on my drive tonight with staging lady in there new van. They have just gone to bed but dave is an electrical engineer, I will ask him in the morning if he can make any sense of it.
     
  16. dazzer

    dazzer Read Only Funster

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    If i were you id stop wasting any more time trying to find the fault and just fit a new wire from the white brake switch wire to the rear brake lights or even try and find the original wire fitted when it was converted to UK spec and connect a new feed onto that :thumb:

    You could be there for hours and having no idea what does what a new start could be the easiest solution all round :Wink:
     
  17. pappajohn

    pappajohn Funster Life Member

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    do your brake lights usually work with ignition off ?

    if so do they work now with ignition off ?

    you're getting a voltage in the white with ign off so it should light the lights.

    the 4.4v in the white with ign on is a puzzle as is only 11.6 with ign on.

    ign on will be a higher battery drain so the 11.6 isnt too worrying but it seems there is some kind of backfeed from the ign to the switch get a 4.4v reading without the pedal pressed. (brake switch open)

    what readings are there if the engine is running ?
     
    Last edited: Sep 8, 2009
  18. quicksam

    quicksam Read Only Funster

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    Earth fault

    Hi Bryan,
    my therory is that you have a loose/broken earth wire on your van.
    When the toad is plugged in you are completing the circuit through the toads circuits and the vans lights will work.
    Worth looking eh ?

    cheers
    Sam
     
  19. Bryan

    Bryan Read Only Funster

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    Thanks for the replies :BigGrin:


    Cheers Paul :thumb:

    I have considered this but I cannot be sure that the white wire goes just to the brake light directly...If I put a new wire in I may bugger summat else up :Doh:

    Will check with engine running tomorrow...
    Can't remember if they work with ign off - but suspect they do, usually, but at the moment NO brake lights work...On the RV or the toad (scotchlok'ed from light cluster methinks.)

    when i press the brake on the toad it sends the power up the cable to the lights via the scotchlokd connections so wouldn't the bad earth stop that working too?

    Thanks
    Bryan
     
  20. pappajohn

    pappajohn Funster Life Member

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    beaten me Bryan without being there......maybe need a grownup to look at it.:Doh:
     
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