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Smoked my brake reservoir!

Discussion in 'Mondial' started by blownfuse, Jan 7, 2020.

  1. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
    2,149
    Berkeley, CA
    Full Name:
    Brian Brown
    The brake fluid reservoir has floats with magnetic reed switches that turn the brake warning light on and disable the ABS system if the fluid level is too low. Brake fluid is not going to short out the switches or wires in the connector on the reservoir. Have you disconnected the connector on the fluid reservoir and inspected the contacts? Have you pulled back the rubber boot on the connector and inspected the wiring?

    If any of the connectors/wires are heat damaged, my guess is that the new fuse board is wired incorrectly and sent power and ground to the normally closed set of switches, causing a short circuit and the heat damage that you experienced.

    All of the cars that use the same Teves ABS system (Ford Thunderbird, Alfa Romeo, Jaguar) have the same switch setup in the reservoir. One switch is normally open when the fluid level is good. When the fluid level drops too low, the switch closes and the "Brake Failure" warning light is illuminated. There is a 10 ohm resistor in line with this switch, so if you test the switch function, when it is closed (low fluid level) you should measure 10 ohms between pins 3 and 4 on the reservoir connector.

    The other switch is normally closed with good fluid level. When the fluid level drops very low, this switch opens causing the ABS to stop functioning and the ABS warning light to come on. With a good fluid level you should measure close to 0 ohms between pins 1 and 2 on the reservoir connector. Pin #5 on the connector is not used. Pin #1 is at the left side of the connector on the reservoir and pin #5 will be on the right side (if you pull the rubber boot back on the harness connector, you should see no wire going to the pin #5 opening.

    I would make some measurements and inspect the connector/wiring. I bet that you will find heat damage to the switch that is normally closed (pins 1 and 2).
    All of the other manufacturers only use two micro-switches in their reservoirs, but Ferrari uses 4 switches (probably has two sets of floats with two switches on each float). The two that are normally closed are wired in series, and the two that are normally open are wired in parallel with the 10 ohm resistor connected to the ends of both switches. For all practical purposes, you can just make the measurements at the reservoir connector as if there were only two switches inside.

    The 348 repair manual has a good description of the system/reservoir switch function, as well as the Ford, Alfa Romeo and Jaguar manuals.

    Brian Brown
    San Francisco Motorsports
     
    blownfuse and moysiuan like this.
  2. blownfuse

    blownfuse Karting

    Jul 16, 2012
    91
    Campbell, California
    Brian you're an amazing resource, thanks! I finally got some time to make the measurements. Don't see any damage to the connectors, and I gave them a thorough cleaning with some contact cleaner.

    I measure less than one ohm here.

    I measure less than one ohm here too.

    As an additional diagnostic I started the car with the float switches unplugged, and all warning lights turned off (even ABS). Plugging in the float switch, the "BRAKE FAILURE" light illuminates.

    It appears as though I may have welded one of the float switches closed. Don't know if the switch is reparable, as it seems only the entire braking unit (reservoir + cylinder) is listed in the parts catalog.

    Will drain it of fluid and see if I can extract the switch later this week. Sure don't want to pay the hefty price.
     
  3. moysiuan

    moysiuan Formula 3
    Silver Subscribed

    Nov 1, 2005
    1,734
    Toronto, Canada
    Full Name:
    Andy
    Not sure this will help, but these are some of the other cars that had the Teves II ABS available as an option...

    TEVES MARK 2 ABS (4-wheel, Integral)
    1985 to 1989 Lincoln Continental
    1985 to 1992 Lincoln Mark VII
    1986 to 1989 Buick LeSabre
    1986 to 1990 Buick Electra, Park Avenue
    1986 to 1989 Cadillac Fleetwood Brougham
    1986 to 1990 Cadillac DeVille
    1986 to 1990 Oldsmobile 98
    1986 to 1990 Pontiac 6000 STE
    1987 to 1992 Ford Thunderbird
    1987 to 1992 Mercury Cougar
    1987 to 1993 Saab 9000
    1988 to 1989 Cadillac Eldorado, Seville
    1988 to 1989 Buick Reatta, Riviera
    1988 to 1989 Merkur Scorpio
    1988 to 1990 Oldsmobile Delta 88, Toronado
    1988 to 1991 Peugeot 505
    1988 to 1990 Pontiac Bonneville & SSE
    1991 to 1993 Saab 900
    1991 to 1993 Volkswagen Passat
     
  4. moysiuan

    moysiuan Formula 3
    Silver Subscribed

    Nov 1, 2005
    1,734
    Toronto, Canada
    Full Name:
    Andy
  5. blownfuse

    blownfuse Karting

    Jul 16, 2012
    91
    Campbell, California
    You're darn right that's a help! Was starting to scan local junkyards for Jaguars and Lincolns... :)
     
  6. blownfuse

    blownfuse Karting

    Jul 16, 2012
    91
    Campbell, California

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