550 no brake lights | FerrariChat

550 no brake lights

Discussion in '456/550/575' started by bill59, Jun 7, 2025.

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  1. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    bill h
    Well, my 550 finally arrived yesterday. A real beauty. It’s been 10 years since I drove one! But I show up for the inspection and the brake lights don’t work. Apparently they flash when the fob is pushed (inspector said that). Fuse is ok. Bulbs ok. The brake switch itself has two red wires running to it into the same contact and one blue wire. I’ve read nightmares about getting the switch positioned correctly so I haven’t tried to remove it. Does anyone have a suggestion how to test the switch? Bill\
     
  2. Qavion

    Qavion F1 World Champ
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    #2 Qavion, Jun 7, 2025
    Last edited: Jun 7, 2025
    Usually there is a grounding issue if you have issues like that.

    Anyway, first check for voltage at the light connectors:

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    The red wire is the brake wire. You'll need someone to push on the brake pedal (with the key turned on). The red/black wire is reverse. The black wire is ground. Check continuity to a good ground on the chassis (let us know what the resistance value is). It should be close to zero ohms. Unfortunately, the wiring diagrams don't show the location of the ground for the brake lights.

    If no voltage at the lights, you'll have to check the switch. Can you take a photo of the wiring on the pedal switch? The wire colours disagree with the Ferrari wiring diagrams, but I suspect the blue wire is key power from fuse 22 and the two red wires go to the brake lights and ABS system. Remove the switch plug and check for voltage on the blue wire (key on). You may also be able to check across the switch pins for continuity with the brake pedal pushed. Should be zero ohms.
     
  3. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    bill h
    Thanks for the detail. I’ll do it today.
     
  4. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    I just checked at the brake light. It’s 37 ohms. The ground was at the battery. I checked the backup light with car in reverse and it was the same. Onto the brake switch? Thank you. Bill
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  5. Qavion

    Qavion F1 World Champ
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    That doesn’t make sense at all. I don’t know what you’re checking.

    Remove the tail light plug and check the red wire for voltage, not resistance. I mean check the plug half that has just come off in your hands. You’re looking for 12 volts between the red wire and the chassis/body with the brake pedal pushed.

    Then, in resistance mode, check between the black wire on the plug and the body. If that is 37 ohms, that is a big fail. Is it the same on both sides of the car?

    What do you mean by “the ground is on the battery”? The ground for all the tail lights should be somewhere in the trunk/boot.
     
  6. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    bill h
    I know it doesn’t make sense. I believe I misunderstood about checking resistance versus voltage. I put a wire to the ground on the battery to make sure I had a good ground to check with. Apparently what you’re saying is that I should find a place to ground in the trunk. That may necessitate scraping some point off as I didn’t see an obvious place to be confident I had ground.

    I have checked for voltage to the red wire with brake engaged. There is none.The resistance between the black wire and a ground at the battery is 5.6 ohms. If I need to be on the body and not the battery for ground, I’ll redo. I have not checked the other side but I will do that.

    I will rerun things in the morning. thank you for your patience. Bill
     
  7. Qavion

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    Isn’t there a metal piece on the trunk latching mechanism?

    That still seems rather high. Good grounds should be 0.2 ohms. One ohm is reasonable. Is the battery at the front or rear of the car? Did you use a long piece of wire as part of your test equipment? Maybe your test lead connections aren’t the best? Or maybe your battery terminals need cleaning.

    So that’s a fail also. Was the key on?
     
  8. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    Key was on for voltage checks. With the battery in the front of the car, wire from battery ground to rear tail light area is 6+ feet. I will recheck everything tomorrow.
     
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  9. Qavion

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    #9 Qavion, Jun 8, 2025
    Last edited: Jun 8, 2025
    Sometimes if you use cheap crocodile clips on test leads, they can add too much resistance. Try measuring the resistance of the test lead.

    By the way, is "bean town" Boston? I don't know if your car is a USA car or Europe car. They have different wiring.
     
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  10. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    Thanks for the tip on the alligator clips. I’ll test the lead. Just sitting here at 7AM, it seems logical to me, that with taillights and back up lights working (but no brake lights or third brake light), it must be the switch. Perhaps someone can tell me why not jump to that test and get it out of the way? Other than I don’t see how to get it apart.

    beantown is Boston. I am now north of Boston and 1 1/2 hours by interstate to the closest shop I trust. I am very hesitant to drive without brake lights. We’re not called Massholes for nothing.
     
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  11. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    bill h
    I forgot to add that I have a 1998 USA model.
     
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  12. Qavion

    Qavion F1 World Champ
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    Well, if we go by your mechanic's report, the brake lights come on with the turn lights, so you may have two issues. Of course, he may have been seeing some kind of reflection off the turn lights. Do the brake lights come on with the turn indications?

    Do you mean pull the plug off or pull the switch apart. I think most people just replace them because they're relatively cheap.

    Anyway, if you have a bit of wire like a test lead, you can always short out the blue wire to the red wires on the connector to see if the brake lights come on. i.e. with the key on.

    By the way, if you push on the brake pedal, is there an air gap between the switch plunger and the brake pedal arm?
     
  13. Qavion

    Qavion F1 World Champ
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    Make sure you have enough travel on the brake pedal before you go adjusting or replacing the switch

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    I don't recall seeing a switch clearance value for the 550.
     
  14. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    I’ll test the brake light going on upon starting the car. At the time he observed this, the tail lights were on. I was skeptical, but he’s a good mechanic.

    I was thinking of trying to separate the switch to get access to the wire connectors. Looking at my photo, on the right in the middle of the black section, there is an indent with some white peaking out. I was thinking that might be a release tab. I am very wary of this switch. I don’t have a high confidence level I could replace it and get it right. If I read your diagram correctly, the 99.5 must be mm. So that’s just less than 4 inches of travel. I’ll have to check. Off hand I don’t think the pedal currently has that travel set up.

    I’m off to spend some time on the car. My wife has begged off pushing the pedal, as it is a tough push for her. If I can’t test at the switch I am stymied for now.
     
  15. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    I jumped across the brake switch and the rear brake lights, including third brake light, illuminated. Key was on of course. Also when key is on I have a solid 12+ volts from just the blue wire. However I have a max of two inches travel on the brake pedal. I find it interesting that most of the fasteners, including at the brake switch, have been painted yellow and it looks like none of them have ever been removed since the paint. It looks like it must have at the factory.
     
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  16. Qavion

    Qavion F1 World Champ
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    Can you tell if this 2 inches is enough for the switch plunger to extend fully?
     
  17. Qavion

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    #17 Qavion, Jun 9, 2025
    Last edited: Jun 9, 2025
    I'm wondering if other 550 owners can chime in here. Is the brake pedal supposed to be this hard. How much does the behaviour change with the engine running?

    Have you pressed the pedal so much, it's just firming up?

    If you can adjust the switch to clear the brake pedal when the pedal is pushed in 2 inches, this will be a temporary fix until you can establish whether the brake system is operating normally? I guess you'll need a couple of suitable spanners (or you might be able to get by with one).

    Ouch... I see that the workshop manual says that the brake pedal rod should never be adjusted. It says that you have to replace the whole master cylinder brake booster unit (not just the cylinder) as the travel is set up at the factory.
     
  18. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    bill h
    Your comment on the pedal firming up without running the car is excellent. I’ll start it, maybe give it a short drive tomorrow, and see what happens. The brakes seemed fine to me when I drove it on Friday. I’ll have to be under the dash to see about plunger extension. With the fasteners painted I can only assume somebody did the right thing initially. But I’ll try to figure out travel on the plunger tomorrow after starting the car. Thanks.
     
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  19. Qavion

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    I don't know if the paint is there to show the switch has been adjusted or to show if the switch has moved from that adjustment. Hopefully you don't have to fight Loctite or some other sealant during removal.
     
  20. 71veedub

    71veedub Formula Junior

    May 31, 2006
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    That seems to implicate the brake switch, don't you think Ian @Qavion?
     
  21. 71veedub

    71veedub Formula Junior

    May 31, 2006
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    I should probably climb up on a ladder and look at mine because I'm probably confused, but why is that relevant? The switch should close almost immediately upon starting to press the brake pedal?
     
  22. bill59

    bill59 Karting

    Oct 26, 2010
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    bean town
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    The plunger fully extends upward when depressing the brake. There’s a good 1/16 and maybe an 1/8” between the arm that the plunger works against and the plunger. Also, the brake pedal didn’t relieve much, if any after a short drive. I might be able to replace the switch but the seat has to come out. I don’t know what that involves. It’s not the kind of space in the footwell I relish.

    I am pretty certain the paint is factory. It’s on the pedal support fasteners and others in the area.
     
  23. bill59

    bill59 Karting

    Oct 26, 2010
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    I agree.
     
  24. bill59

    bill59 Karting

    Oct 26, 2010
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    I see one part number for the switch—-133555. Anybody have any doubts that’s the right part?

    I also need to buy a switch for the hand brake (I assume). The “PARK” light remains on all the time.

    I told the young man twice who did the work in AZ it’s the little things that will get him with Ferrari drivers as much as anything.
     
  25. Qavion

    Qavion F1 World Champ
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    That’s the primary issue. It’s just the other odd behaviour that can’t be explained by a faulty switch.

    Understood. I was just trying to determine if there was any clearance at all. If the switch doesn’t disengage from the brake pedal when pushed, you know the adjustment is bad, but you don’t know if the switch is also bad.

    Normally a value is given in the workshop manuals for the amount of push you should have on the switch plunger with the brake pedal released. You don’t want it to be too sensitive.
     
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