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Brake light fuse blowing

Discussion in 'Fuel System & Electrics' started by Sarge, Dec 30, 2019.

  1. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    Auto elec gurus.

    My brake light fuse blows as soon as I turn the ignition on. I know it has a short somewhere and I’ve searched for a short to earth on all the wires without success. When I put a multi meter over the wires, both ends of the fuse, I get resistance. Even when I put the multi meter over both wires to earth and one wire to the other, same result. Could this mean it is one of the brake light switches that is causing the fuse to blow? Or am I just doing some wrong?
     
  2. Barry

    Barry Well-Known Member

    Messages:
    4,849
    Location:
    Abbotsford NSW
    Has it only just started doing this?
    My guess is it is shorting in the brake switch.

    Power goes to the fuse then the brake switch then light then to earth

    Have you checked resistance when the switch gets pressed
     
  3. galp

    galp Member

    Messages:
    81
    Location:
    ulverstone
    Is it a splitty? Had the same deal in mine with the park light globe rattled sideways in its holder inside the headlight making a dead short
     
  4. Barry

    Barry Well-Known Member

    Messages:
    4,849
    Location:
    Abbotsford NSW
    Also what is your definition of resistance?

    Guessing a brake light is ..... 48w ( makes it easy) so you should see 4 ohms to earth, when you press on the pedal, if you take the fuse out and go from the non power side of fuse to earth.
     
  5. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    72 Lowlight.
    It did it intermittently previously and I found some dodgy wiring at the lights which seemed to fix it, but it only blew when the pedal was depressed. So that could have also have been switch related.
     
  6. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    It is showing resistance without any pedal. The fuse blows as soon as the ignition is turned on.
     
  7. tintop

    tintop Well-Known Member

    Messages:
    730
    Location:
    Canberra
    try to eliminate bits as you go...start with the easy bits...pull the wires off the brake light switches and see what happens...take the globes out and see what happens etc.
     
  8. Wayne murray

    Wayne murray Well-Known Member

    Messages:
    3,780
    Location:
    Seven hills
    Is it fuse 12 blowing?As one wire for the ignition runs from fuse 11 backs up to the unfused side to fuse 12. If it's shorting out across one of the other circuits.
    What comes into fuse 12,comes from the positive side of the coil. Black wire.
    If you have or got someone to do work on the rear brake light area, it could be the place to start looking as a short might be there consider work has been done recently there. Something may of been knocked out of place while adjusting dodgy wiring.
     
  9. grumble

    grumble Well-Known Member

    Messages:
    1,184
    Location:
    Taree
    Does it have a Utilux 5 pin plug for a trailer? If so the screw that holds the terminal block has probably fallen out and the brake light pole is shorting to the lid.
     
  10. David H

    David H Well-Known Member

    Messages:
    6,074
    Location:
    newcastle
    Now that's experience a few times over;).
    Cheers
     
    grumble likes this.
  11. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    Thanks all for the responses. I replaced both brake light switches and she’s fixed. Simple fix really. Don’t know why I didn’t do it earlier.
     
  12. oldman

    oldman Super Moderator Staff Member

    Messages:
    9,547
    Location:
    Avalon Beach NSW
    So often the case, simple IS the fix !
    Great outcome.;)
    Cheers,
    Mark
     
  13. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    Yep, simple fix, but now my starter is on the way out. This is why we love out kombis so much!
     
  14. Barry

    Barry Well-Known Member

    Messages:
    4,849
    Location:
    Abbotsford NSW
    Make sure you do the bushing in the bell housing at the same time or use a Wosp (bushless starter)
     
    oldman likes this.
  15. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    Where is the top bolt for the starter? I’ve undone the bottom one, and what I thought was the top one but it not coming out.
     
  16. tintop

    tintop Well-Known Member

    Messages:
    730
    Location:
    Canberra
    engine compartment
     
  17. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    Delete. Inside the engine bay. Better put that bolt back in before something falls out.
     
    Wayne murray and oldman like this.
  18. Barry

    Barry Well-Known Member

    Messages:
    4,849
    Location:
    Abbotsford NSW
    Top bolt doesn’t have a head but rather a”fat disc” with a flat side that catches against the starter.
    As said - nut inside engine compartment.

    Bottom one on stud. Nut gearbox side

    826E3503-A41A-4E2F-B529-717BC3B655B6.jpeg
     
    Sarge and David H like this.
  19. Sarge

    Sarge Member

    Messages:
    86
    Location:
    Falls Creek NSW
    Cheers, I’ve removed and bench tested. She’s stuffed. Off to pick up a new one tomorrow.
     
    Barry likes this.
  20. cbus

    cbus Well-Known Member

    Messages:
    12,799
    Location:
    sunshine coast
    Was shaft supported when bench tested( if not a supported starter?)
    ie auto is supported.
    Manual usualy not.
    Also wosp startersfrom jk nice upgrade.
    https://www.justkampers.com.au/search/result/?q=WOSP
     

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