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Brake fuse blow

Discussion in 'Land Rover Freelander' started by JulienV, Oct 3, 2016.

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  1. JulienV

    JulienV New Member

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    Hi there.
    my brake/reverse fuse blow each time I press the brake pedal.
    not blow when reverse...
    Any idea?
     
  2. freelance

    freelance Well-Known Member

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    Either a chafed wire, or more likely the switch
     
  3. JulienV

    JulienV New Member

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    I have test the switch...
    pin 1 and 3 in contact when not press
    pin 1 and 2 in contact when half press
    pin 1, 2 and 3 when full press...
    is it OK
     
  4. JulienV

    JulienV New Member

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    forgot to tel that 3 amigos are with me...
     
  5. gstuart

    gstuart D3 Grandad

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    yep need a new brake light switch if u have the 3 x amigos

    is normally the first thing to replace

    will have a small additional wire, it's just a conversion cable to take u between the loom and the new switch

    have to drive up the road after it's been fitted and lights should then go out
     
  6. GrumpyGel

    GrumpyGel Well-Known Member

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    The switch looks to be working - I presume that's what it is supposed to do. Isn't it more likely to be a chafed wire or a light that is blowing the fuse.

    The blown fuse is almost certainly what is raising the Amigos (eg no current with which to test the switch), but even so it might be worth putting a code reader on it. If you replace the fuse and turn the ignition on (without pressing the brakes!) do the Amigos go out?
     
  7. Joe_H

    Joe_H Well-Known Member

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    From a quick look at the diagram for the later vehicles -

    On the 3 pin switch pin 1 is a live feed from F2.
    Pin 2 is an output to the ABS ECU (High active - brake on)
    Pin 3 is the supply to the brake lights when the switch is pressed.

    You should have (if the switch is off the vehicle)
    continuity between 2 and 3 at all times. (as they are connected together in the switch according to the diagram)
    Continuity from 1 to (2 and 3) when the brake pedal is pressed.

    You readings seem totally wrong - although that would not blow the fuse.
    It sounds like you have a short circuit in the output feed to the brake lights (wiring short to ground) - or more likely at one of the light fittings themselves.
    Note - If you have a trailer socket fitted also check the wiring here as a problem in that area can be common.

    As said, the switch should never blow the fuse regardless - the worst case with the switch failing is the brakes are on all the time or off all the time.
    I think you need to check your readings again. - with pin 1 and 3 connected at all times the brakes would be on at all times.
    As you say the brake fuse blows when you press the switch, it would appear that there is no continuity between 1 and 3 when the switch is NOT pressed ( - you say there is - ) - if there was, the brakes would be on without pressing the pedal.
    As the fuse is blown WHEN you press the switch that indicates that the switch IS switching the live feed tot he output. - hence - I would presume the switch is fine and that your readings are incorrect. - the readings you have taken and the description of what happens that you have given are completely opposing.

    brakeswitch.jpg
     
    Last edited: Oct 4, 2016
  8. GrumpyGel

    GrumpyGel Well-Known Member

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    That's not right Joe. The diagram for the brake switch does show a direct link between pins 2 and 3 - but that is not the case. If you follow the wires from Pin 3 they go via a header to the brake bulbs - but also to the ABS ECU as well as Pin 2 - so they must have a different use.....

    Checking the pins these 2 wires go to on the ABS ECU - the one from Pin 2 goes to 11 on the ECU and is described as "Brake switch (BTS contacts)", the one from Pin 3 goes to 18 on the ABS ECU and is described as "Brake switch (BLS contacts)". The BLS one is the one the ECU uses to know the brake peddle has been pushed. The BTS is a startup test. More from Rave...

    "A mechanical brake pedal switch is used to illuminate the stop/brake lamps on the vehicle because of its high current carrying/switching capabilities. It is also used to input the status of the brake pedal to the ABS ECU. This switch is a double contact switch where the Brake Lamp Switch (BLS) contacts are open and the Brake Test Switch (BTS) contacts are closed when the brake pedal is at rest. When the pedal is depressed, the BLS contacts close and BTS contacts open, supplying 12 volts to the brake/stop lamps and indicating to the ABS ECU that the pedal has been operated. When the pedal is depressed there is a time when both the BLS and the BTS contacts are closed, which allows the ABS ECU to perform a plausibility check on the switch. The switch used is a carry over from the Range Rover."
     
  9. GrumpyGel

    GrumpyGel Well-Known Member

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    So Pin 1 is the feed from Fuse 2.

    "at rest", only Pin 2 should be live.
    When open a little, both Pin 2 & Pin 3 should be live.
    When fully open, only Pin 3 should be live.
     
  10. Joe_H

    Joe_H Well-Known Member

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    Hi GG, I missed the link from header 0287 back to the ECU (the one from pin 3 !)
    Well spotted and thanks for correcting me - also apologies to the OP for incorrect info. :( -- doh ! :)

    There is still no way the switch itself can blow the fuse though - and as you pointed out originally - the switch appears to be working as it should.
     
  11. Nodge68

    Nodge68 Well-Known Member

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    I'd be looking at the bulbs before doing anything more in depth. It's no unheard of for a bulb to short after it's failed.
     
  12. JulienV

    JulienV New Member

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    So.
    I read you all...
    I'm a little bit lost (it's normal I'm french...)
    My brake switch is OK?

    The Bulb is OK they light on my Clio MK1 and don't blow the fuse of the clio...
    The holder bulb is Ok but previous owner did a repair at 1Cm on the 3 Wire of the left holder bulb 2 contact...
     
  13. Nodge68

    Nodge68 Well-Known Member

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    Have you checked the high level brake light and it's wiring. I've seen the wires pinched in the fitting in the past.
     
  14. gstuart

    gstuart D3 Grandad

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    i done that when i painted the wheel carrier, but luckily noticed that i had pinched the wire

    before putting in a new brake pedal switch i tried to repair the old one, but it just fell apart

    did always assume when the 3x amigos showed up it was the brake light switch but can see its more involved in this circumstance
     
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