'86 Mondial Cabrio Stop lights won't work | FerrariChat
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'86 Mondial Cabrio Stop lights won't work

Discussion in 'Mondial' started by ainternetguy, Jun 6, 2010.

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  1. ainternetguy

    ainternetguy Rookie

    Oct 16, 2005
    21
    #1 ainternetguy, Jun 6, 2010
    Ok, so I took the cabrio out for a spot of Gelato (new Italian bakery down the street) and now the brake light warning light lights up on the center console warning cluster, and the brake lights (neither the center one nor the lateral ones) light up.

    What gives? With the car off, I can push the brake pedal and hear the micro switch, but somehow, no power to the lights.

    Fuse is OK. Don't see a relay for the brake lights, nor do I find one on the schematics.

    Temperature was 99 degrees on the day that the car did this, so I figured hot temp, hot soak (stopped for about 30 minutes for the Gelato).. and possibly something got hot and lost connectivity.

    Any suggestions appreciated.

    Thanks
     
  2. Paul_308

    Paul_308 Formula 3

    Mar 12, 2004
    2,345
    #2 Paul_308, Jun 6, 2010
    As I read your post, when pressing the brake pedal, the brake lights don't come on but the brake warning light does. Two separate problems actually.

    1) The warning light can indicate low brake fluid in either reservoir or uneven brake pressure in the proportioning hydraulic circuit, most often the former.

    2) Brake microswitches do go bad and should be check by unplugging the connector and carefully shorting the two terminals, then check illumination of the brake lights.

    Very possibly your brake lights have been out for some time and you only now noticed it because your brake fluid is now low, bringing your attention to the brakes.


    __________________________
    http://www.FerrariDiagrams.com
     
  3. ainternetguy

    ainternetguy Rookie

    Oct 16, 2005
    21
    #3 ainternetguy, Jun 7, 2010
    Thanks Paul,

    Actually, I check all the circuits regularly and the brake lights have been working. I'll check the fluid level tonight (I check fluid level regularly too, but this may have slipped past0.

    As for the microswitch, I can hear it but can't see it.

    Where is it located and do I have to be a contortionist to get to it?

    Mike
     
  4. Scaledetails

    Scaledetails F1 Rookie

    Nov 19, 2003
    4,211
    Daytona Beach, FL
    Full Name:
    Stephane
    #4 Scaledetails, Jun 7, 2010
    This happened on my 86' Mondial, and I couldn't figure it out, all the connections seemed fine along with the fuses. My mechanic found the problem. The connection inside the front trunk was burned (located just ahead of the steering column position), so he replaced that "relay?" with a new one from Pep Boys.
     
  5. Lenvo65

    Lenvo65 Formula Junior

    Apr 3, 2005
    293
    Bergen Cty NJ
    #5 Lenvo65, Jun 7, 2010
    '86 mondial 3.2 cab as well. I need to take the car off the lift and look later in the week for exact location, but remember it not being a big deal at all to take out. It should be on the firewall, near the master cylinder, with three wires on it. Unplug the wires and unscrew it from the front trunk side of the firewall. You should note how many turns it takes to take it out so that when you put the new one in you have some kind of baseline on adjustment.
     
  6. Paul_308

    Paul_308 Formula 3

    Mar 12, 2004
    2,345
    #6 Paul_308, Jun 7, 2010
    The clicking sound of the switch gives reassurance the switch exists but not that it works.

    In 308 cars, the brake stop light switch is located under the dash on a bracket immediately above the pedal. Others mentioning a faulty device near the master cylinder are probably referring to the hydraulic switches which monitor fluids for the warning light, not the brake light switch.
     
  7. ainternetguy

    ainternetguy Rookie

    Oct 16, 2005
    21
    #7 ainternetguy, Jun 7, 2010
    OK, so I looked under the hood, just in front of the firewall on the brake booster block and checked the switch. Disconnected the wires (4 leads). Verified power from the leads and had voltage. Bridged the green and red and brake lights light up. Looks like the switch is toast (or at least intermitent). The other wires (smaller gauge) activate the panel warning light (brake lights not working). That portion of the switch is still working......however.

    In any case, i've got to buy a 4 prong switch.

    T. Rutlands and Ricambi have the 2 prong from about $7 plus shipping. 4 prong (which is what I have in this '86 Cabrio is $117 at Rutlands and $101 at Ricambi!!!! Does 2 extra terminals add more than $90 to a switch? WOW.

    Any ideas? What does this switch come from? I know my mirror switch is a BMW 5 series piece. Could it be that this is also a BMW piece as well? Any pointers appreciated.

    Also, thanks for the previous posts on this... you got me pointed in the right direction!

    Mike
     
  8. Paul_308

    Paul_308 Formula 3

    Mar 12, 2004
    2,345
    #8 Paul_308, Jun 7, 2010
    No.

    But this has been interesting to try understanding the mentality of the engineers. Do they actually feel they add value or safety or ?? to the car by adding the second switch section which simply lights a warning light as opposed to using a more reliable, more substantial and longer lived switch.

    I would be tempted to rework the bracket and connector to use parallel 2 separate switches. It's not a concourse inspection area.

    Can you post a picture of the switch and perhaps an exact substitute will emerge?
     
  9. ainternetguy

    ainternetguy Rookie

    Oct 16, 2005
    21
    #9 ainternetguy, Jun 8, 2010
    Last edited by a moderator: Sep 7, 2017
  10. ainternetguy

    ainternetguy Rookie

    Oct 16, 2005
    21
    #10 ainternetguy, Jun 15, 2010
    Any ideas on if there is a cross-part or alternate source for this switch? BMW, FIAT, Others?

    Thanks

    Mike
     
  11. flyngti

    flyngti Formula 3

    Jul 16, 2009
    1,246
    Snohomish, WA
    Full Name:
    Eric L
    #11 flyngti, Jun 16, 2010
    My 308 2-terminal switch had overheated and melted and I replaced it with one of these:

    http://www.summitracing.com/parts/PRF-80172/

    They make a 4 terminal version as well:

    http://www.summitracing.com/parts/PRF-80176/

    I have no idea whether the additional terminals will work the same for your application, but it may be worth a shot for < $15. It's not a plug and play though -- I needed to add some plastic to the end to extend the button end and run a metric die down the body to cut new mounting threads. It was additional work but I feel like this replacement is more substantial than OEM.

    A bit more detail on what I did here:

    http://f308.blogspot.com/2009/10/working-brake-lights.html
     
  12. ainternetguy

    ainternetguy Rookie

    Oct 16, 2005
    21
    #12 ainternetguy, Jun 16, 2010
    Thanks for the pointers.

    This afternoon, before reading this post, I took it upon myself to pull the old one out and take it apart (quite easy actually).

    I saw that the microswitch looked dirty and the plunger dragged a little in the sheath. A little contact cleaner / lube (Radio shack) and I put it back together and tested it. VOILA.. it works again.

    Seems the contacts where dirty. Switch came apart easily (too easily for my liking). I put it back together and added a little clear RTV sealer to the outer diameter of where the micro switch and housing come together.

    Let's see how long it holds, but for now... the Cabrio is road ready!!! (now if I could only get the ambient humidity down below 1000%, it would be great to drive with the top down without the A/C on MAX).


    Mike
     

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