Lusso brake light trouble shooting

Discussion in 'Vintage (thru 365 GTC4)' started by gimmea250swb, Nov 23, 2017.

  1. gimmea250swb

    gimmea250swb Formula Junior
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    Mar 8, 2007
    479
    Washington, DC
    Full Name:
    Taylor
    Hi, I'm at home helping my dad with his Lusso. I can't get the brake lights to work.

    I've checked the switch - when the pedal is pressed the switch closes.
    I've checked continuity from the light to the switch.
    I've jumped the light from the driving lights to the brake lights and confirmed the bulbs are good.

    The part I can't figure out is the continuity from the switch to the fuses. I'm using a digital multimeter. If I connect from the lead at the switch (disconnected from the switch) and the terminals at the fuse box I get a closed circuit to nearly all of the terminals of the different fuses. This doesn't make sense to me, but it's what I'm seeing. Is there some electrical wizardry I don't understand - why does it seem like all the fuses are connected??

    The car runs, the headlights and foglight work fine.
     
  2. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
    1,451
    Berkeley, CA
    Full Name:
    Brian Brown
    I would measure voltage instead of continuity. Do you have 12v at the input side of the brake light switch? If not, you will have to go back to the fusebox and see if you have 12v at both sides of the fuse that supplies power to the switch. When you press the brake pedal, do you have power at the outlet side of the switch, if not there is a problem with the switch, if so then there is a supply problem to the brake lights. All of the test should be performed with the brake pedal depressed, as this puts a load on the system and will reveal where the break/resistance in the circuit is located.
    Some of the fuses have the supply side bridged together, as some are powered all the time and some are powered with the key on. The output side of the fuses are separated. Don't use continuity to find the problem, use either a test light or a voltmeter.
     
  3. afwrench

    afwrench Formula Junior
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    Nov 24, 2004
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    NY
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    Mike
    Hi Taylor. Do the turn signals work? Most brake lights feed in some way through the turnsignal switch/flasher system so they will flash when the pedal is pushed.Trace back from the brake lights to the common points at or near the dash .Good luck,Mike
     
  4. gimmea250swb

    gimmea250swb Formula Junior
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    Mar 8, 2007
    479
    Washington, DC
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    Taylor
    Hi Mike and Brian,

    Thank you both for your replies. The solution was much easier than I was making it out to be. I checked voltage on both the fuse and the wire at the switch and it had voltage. It turns out the bullet connectors were a little dirty so I sanded them. I also pushed them into the switch hard to ensure they were making a connection. The lights are working now!! It was fun working with dad trying to figure it out.
     
    Caeruleus11 likes this.
  5. afwrench

    afwrench Formula Junior
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    Nov 24, 2004
    356
    NY
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    Mike
    Hi Taylor ,so glad you got it fixed. So many times it is something simple and a systematic approach will yield a solution.A great feeling when an electrical problem is solved. Mike
     

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