Tech question: Brake warning light

Discussion in '308/328' started by Tokyo Drftr, Aug 9, 2009.

  1. Tokyo Drftr

    Tokyo Drftr Formula 3

    Jan 18, 2009
    Full Name:
    Did the 80's gtbi have any problems with the brake warning light coming on? Did a full brake inspection and all is good, even checked my bulbs just incase. Had one bad bulb. Anyway i will check the fluid level sensors when i get time. But was wondering if this was an associated problem with these cars. Thanks.
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  3. rizzo308

    rizzo308 Formula 3
    Silver Subscribed

    Sep 12, 2004
    Perth, Australia
    Full Name:
  4. Paul_308

    Paul_308 Formula 3

    Mar 12, 2004
    #3 Paul_308, Aug 9, 2009
    Last edited: Aug 9, 2009
    Each of two reservoir chambers plus the proportioning valve have a switch. There is a brake failure relay whose sole purpose in life is to light the tach's brake warning lamp when the ignition switch is in the start position, proving only the driver's visual circuit, not the cause. Only an informed and alert driver would notice it not lighting. The brake proportioning switch will only work when you have pressure in one line and not the other and this only when the brakes are pressed. The brake failure circuitry wires are pink, among the very few pink wires on the car.

    Any switch or relay can fail but the reservoir switches are the most likely to cause a false warning condition. My 1980 brake light has never failed and I've only seen the occasional thread (one last month), so I wouldn't consider it a common problem like slow windows or fuse panels which are endemic to the 308.

    I should add that some Ferrari's of the '70-'80 period have a single common reservoir switch serving both hydraulic circuits.
  5. Crallscars

    Crallscars F1 Rookie

    Jun 7, 2006
    Bainbridge, GA
    Full Name:
    Douglas Crall
    My 85 the light is on about 75% of the time. The dealer that sold me the car 3+ years ago had a mechanic of some abulity diagnose it as the perportioning valve (sorry no spell check today). The dealer in my case apologized when I went to pick up the car and offered to install the replacement valve if I wouldn't mind waiting for four of five hours, I opted for the part in a plastic bag to start my spare parts collection.

    To check if your problem is the level switch in the master cylinder just disconnect one of the 2 wires connected to the resovior bowl. If it is still could be a bad proportioning valve switch. It hassn't bothere me enough to lift the car, remove the front skid plates and poke around, but it's on the list of things to do.
  6. PittsS2APilot

    PittsS2APilot Formula Junior

    Jun 29, 2007
    Gulfport MS
    Full Name:
    The brake light on my 80 GTBi comes on for about 2 seconds when Im in a hard left turn? Doesn't do it in a right turn though? I guess its the fluid sloshing to the side? Other than that, it stays off any other time. Joe
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