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Brake Warning Light not working

Discussion in '308/328' started by wda24729, Aug 7, 2015.

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  1. wda24729

    wda24729 Formula 3

    Sep 22, 2014
    1,000
    Devon, UK
    Full Name:
    Graham
    #1 wda24729, Aug 7, 2015
    Hi - Ive got my dashboard apart at the moment and wanted to make sure everything was working before I re-assemble but my brake warning light has never worked and wanted to get this working again.

    Im assuming it comes on with ignition and then goes off when started assuming everything is ok. I tested with the multi-meter and haven't got any power to the terminal nor to the switch on the reservoir

    Any suggestions? Thanks
     
  2. wda24729

    wda24729 Formula 3

    Sep 22, 2014
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    Graham
    #2 wda24729, Aug 12, 2015
    Any suggestions before I stick it all back in? I don't like things not working!
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
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    #3 Steve Magnusson, Aug 12, 2015
    Last edited: Aug 12, 2015
    If this is on a euro 308i-2V (please confirm/deny model/version) = no, it doesn't work that way. The OM schematic indicates that the brake warning light in the dash would only come "on" if:

    1. the handbrake is "on" with the key "on",

    2. the brake fluid level is low with the key "on", or

    3. the brake pressure switch detects a pressure imbalance between the dual brake circuits.

    Does the nearby (blue) dash light showing the main (high) beams are "on" work OK?
     
  4. wda24729

    wda24729 Formula 3

    Sep 22, 2014
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    Graham
    #4 wda24729, Aug 12, 2015
    Sorry - US 2V Version.

    I have the parking brake light working on the right of the tacho, its the brake warning light on the left of the tacho not functioning.

    I also pulled the float switch out of the brake fluid reservoir to fake an empty but still didn't come on

    Main beam light (between the two brake lights) working ok.

    Thanks.
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #5 Steve Magnusson, Aug 12, 2015
    Yes, that's a little different operation -- the brake warning light on a US version should also come "on" during starter motor cranking. If it doesn't, try a different ...113 relay in relay position F "Relay for brakes [sic] warning light".

    Having the handbrake warning light work would be a good sign as the +12V power for that and the brake warning light are shared.

    Not sure why removing the brake reservoir cap wouldn't also cause the brake warning light to illuminate (with the key "on"), but, on the schematic, it is sort of an oddball arrangement shown with two switches in series -- so could be that physically removing the cap from the reservoir opens one (non-float?) switch so it doesn't matter if the float switch is open or closed, or are there two floats and only one is removable with the cap? Just guessing - perhaps another US version 2Vi Owner could make a similar test.
     
  6. wda24729

    wda24729 Formula 3

    Sep 22, 2014
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    #6 wda24729, Aug 12, 2015
    Thanks Steve, much appreciated. I don't suppose you have a copy of the wiring diagram?
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
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    #7 Steve Magnusson, Aug 12, 2015
    It's in your OM -- which you can download from All Ferraris
     
  8. wda24729

    wda24729 Formula 3

    Sep 22, 2014
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    #8 wda24729, Aug 12, 2015
    Last edited: Aug 12, 2015
    Oops..never spotted that! I'll give the relays a try in the morning.

    Also wondering where / what Item 103 does in the system

    Thanks again
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #9 Steve Magnusson, Aug 12, 2015
    Item 103 is the switch (item 15) on the brake pressure differential valve (item 16) here (I think):

    Ferrari 308GTBi/GTSi Parts : Table 27 - BRAKE SYSTEM

    In about the 1950s (IIRC), car manufacturers figured out that having a two-channel brake system was way more safe than just a single channel system. However, on a dual channel brake system if one side fails, the brakes still sort of work (which is the whole idea ;)) but it might not be that obvious to the Driver. If the pressures in the two channels get way different, a plunger inside item 16 shifts to one side and close the switch item 15 = turns on the warning light in the dash to let the Driver know that the brake system needs attention.
     
  10. wda24729

    wda24729 Formula 3

    Sep 22, 2014
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    #10 wda24729, Aug 12, 2015
    Ah..so probably not worth tinkering with that then!

    Still baffled with the two switch thing, maybe its two switches inside the reservoir
     
  11. wda24729

    wda24729 Formula 3

    Sep 22, 2014
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    #11 wda24729, Aug 17, 2015
    Sorted..after studying the wiring diagram I noticed an in-line fuse. Eventually found it and it wasn't making a very good connection.

    One thing to note, is that it only illuminates when ignition key is at Position 3, i.e whilst cranking the engine. Traced the wire back to the ignition which confirms this.

    Thanks again for your help.
     

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