Electric Gremlin in 456m | FerrariChat

Electric Gremlin in 456m

Discussion in '456/550/575' started by Drae, Oct 21, 2020.

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  1. Drae

    Drae Rookie

    Jul 3, 2016
    25
    I recently bought a 2000 456m 6 speed...I was driving on the highway, and didn’t see a pothole...bottomed out going about 70mph....was able to continue driving, but lost the dashboard functions and gauges and the power steering went, but was able to continue driving at normal speeds....easily able to get home with zero issues except lost dashboard and gauge functions....thinking that I must have dislodged a wire or something so nothing urgent to address.

    About 5 days later, I am finally able to bring it to garage, car starts easily in my garage.... En route, i stop for gas...car has issues starting, but starts....as I’m driving, I turn the headlights on and it seems to short out the entire electric grid....I lose everything while driving.....dashboard functions, gauges, blinkers, hazard lights , radio....Car starts chugging, going from high speed left lane driving to car slowly dieing as I’m able to get into the breakdown lane....

    Get the car towed to the shop....they are able to turn it on and drive it into the garage...no issues

    We have replaced:
    fuses
    alternator (which needed replacing)
    pop up light engine on the right side
    have looked at the power steering apparatus...

    Drove it again, after fixing these parts....drove for 3hrs in local roads, beautiful drive with radio on, start and stop at several places, no headlights on...absolutely no issues.......Next morning, ready to take long highway trip.....after 30 minutes of high speed driving with the lights on....again, lose the dash function, lights start to dim and go out, and power steering lose again...this time, did not hit any potholes or anything..blew the same fuse that I had blown before and was replaced

    Only thing now seems to be trial and error to continue to narrow the possibilities...car is with a shop used to dealing with temperamental cars of all sorts

    Prior to bottoming out...drove a couple thousand miles with zero issues with anything, let alone electric

    Car is amazing to drive and have no interest except finding the little gremlin that seems to have appeared

    Anyone experienced this before? Any insight is appreciated and thank you in advance.
     
  2. Laserguru

    Laserguru Formula 3
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    Aug 7, 2016
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    Eric
    Wow. I have nothing like this to base an opinion on. Quavion is the most knowledgeable here on the electrical design and issues with these cars. Perhaps an PM to him might be of use. In the meantime, I keep a register of all 456Ms that came to the US. In particular, I track the 95 or so 6-speeds. I have one of the very last to be built and I would be happy to get information about your car from you and share the whole spreadsheet if you are interested. If you give me the last 6 digits of your VIN, I'll see what the Great Karnak already knows about your car!! Welcome to the rather rare 456M GT owners club. They are an amazing blast to drive.
     
  3. Qavion

    Qavion F1 World Champ
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    Has me baffled... still thinking... :D
     
  4. Qavion

    Qavion F1 World Champ
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    #4 Qavion, Oct 21, 2020
    Last edited: Oct 21, 2020
    So perhaps fuse 20 (Instruments, power steering module and airbag). Linked to components with green/white wires.
    This is powered by relay "S". Relay S affects all (?) ignition key powered devices.

    Unfortunately, as the relay panel is floor mounted, it's not likely that relay S came loose with a bump, nor does it explain why a fuse would blow.

    Do you know which fuse was replaced? This may help me track down the problem.

    (EDIT: fuse 20 is also linked to the alternator on a green/white wire for power control)
     
  5. Drae

    Drae Rookie

    Jul 3, 2016
    25
    I believe that is the one, power steering was the focus....but will let u know.....car is still at the shop, being test driven with no issues.....we are attempting to increase the size of the fuse slightly, to absorb whatever maybe going on, but know it’s a temporary fix...so still trying to figure this out.....

    going down the power steering rabbit hole, but the common occurrence has been the lights being on, although last two test drives of 20 minutes or more, lights didn’t impact the car.....
     
  6. Qavion

    Qavion F1 World Champ
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    This reminds me of a defect on a 355 which turned out to be a dislodged magnet in the vertical acceleration sensor (for the suspension system). This might explain why it happened with a bump and why a magnet rattling around in inside the accelerometer might only need slight vibration to trigger the short. It's really hard to get to the acclerometer on the F355 because the bumper has to be removed. Perhaps it's easier on the 456M. The vertical acceleration sensor is powered by that fuse.
     
  7. Drae

    Drae Rookie

    Jul 3, 2016
    25
    Worth a shot at investigating.....will report back....thank u.....
     
  8. Qavion

    Qavion F1 World Champ
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    Here's a rough location of the accelerometer

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    Sorry, the diagram is a little faded, but you might be able to make out the front bumper.

    Here's the wiring from the accelerometer connector (10A) to a connector in the passenger footwell (5D or 19D, depending on which side of the connector you are looking at)

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    Connector 5D/19D is shown in this diagram:

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    If it's too difficult to get to the accelerometer, perhaps your electrician could remove the green/white (VB) wire from plug 5D for further evaluation. You will get a suspension light with this wire removed, but it's only on a temporary basis. You may need a Ferrari SD tool to reset the light after the problem is fixed. I don't think could leave that 5D/19D connector disconnected when driving. There seems to be quite a few things attached to it.

    If you have an active short in the garage however, you could try disconnecting that plug to see if the problem goes away.
     
  9. Qavion

    Qavion F1 World Champ
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    #9 Qavion, Oct 21, 2020
    Last edited: Oct 21, 2020
  10. franschman

    franschman Formula Junior

    Dec 18, 2017
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    Holland
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    Bart
    Suggestion: the steering unit has a sensor the wire of which runs under a chassis part forward. If that is damaged by the grounding, occasionally shorts and blows the fuse, causing the problems mentioned?
    Just a thought.
     
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  11. Qavion

    Qavion F1 World Champ
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    Here's a shot of what I remember was a magnet inside the accelerometer. Now I'm not sure. This solid block is held onto the assembly with some black adhesive.

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  12. Laserguru

    Laserguru Formula 3
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    I'm with you on this. Pondering the issue here, I'm wondering if there is a shared ground post for all these functions. Hit bump, nut comes loose on grounding post....
     
  13. Qavion

    Qavion F1 World Champ
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    Grounding post?

    Grounds shouldn't cause blown fuses. Power wires touching chassis, earth wires, etc, will.
     
  14. Laserguru

    Laserguru Formula 3
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    Personal scar. Once upon a time, in high school, I had a 67 Triumph Spitfire. It had the classic positive earth approach of that era British cars. With the combination of corrosion and non-locking Whitworth threads (why everything fell off MGs and Triumphs and the like), I experienced grounding problems that would cause current surges. It has left me leery of grounding issues. My suspicions aren't "grounded" in knowledge, just psychological scars of British car ownership.
    "Why do the Brits drink warm beer? Lucas refrigerators!!"
     
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  15. Drae

    Drae Rookie

    Jul 3, 2016
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  16. Drae

    Drae Rookie

    Jul 3, 2016
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    thank u. Will pass along and report back!
     
  17. Qavion

    Qavion F1 World Champ
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    For info, 5D/19D is connected to the vertical accelerometer, the right front shock actuator and the oil temperature sender (warning and gauge indications), so, as said earlier, I wouldn't want to leave that connector disconnected when driving (at least not for too long).

    I don't know if your guys have my user-friendly colour wiring diagrams (rather than the workshop manual's hookup diagrams). If not, I would have to send them via email (I can no longer provide weblinks to them).
     
  18. Drae

    Drae Rookie

    Jul 3, 2016
    25
    thank you for all your insight. I will ask
     
  19. asgor

    asgor Formula Junior

    Sep 8, 2016
    705
    Virginia, USA
    Just because no-one mentioned it (and it's probably not the silver bullet but is easy to check), make sure the cables connecting to the battery are tight, fully seated and don't wiggle.
     
  20. Qavion

    Qavion F1 World Champ
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    Whilst this may cause some of the symptoms, I don't see how slightly loose connections would cause a specific fuse to blow.
     
  21. Qavion

    Qavion F1 World Champ
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    I'm curious to know how the pros handle such an intermittent defect. It's not like they could try something and then let you drive it. If they get it wrong, towing fees are not that cheap, and as you said, it's dangerous if it happens on the highway.

    In this specific situation, knowing all the things that are connected to that fuse, I guess they or you could drive around with a bunch of fuses and if the fuse blew, you could disconnect plugs or remove modules until the car started working again. It would simply be a matter of knowing where each plug/device was beforehand. I wouldn't be driving on the highway though for a while.
     
  22. Drae

    Drae Rookie

    Jul 3, 2016
    25
    I have been given some fuses to keep in case happens. But, they have been driving it and testing it out, so hopefully we discover something. Given that it happened twice, and with the help of the brainstorms here. I’m sure we will narrow it down. These guys are used to these types of projects with the cars they work on and have the space to keep it for a while to patiently work through it.

    I don’t plan on driving it until we find it and given the storage season is coming. Not really under much pressure to get it done for this year.
     
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  23. Drae

    Drae Rookie

    Jul 3, 2016
    25
    And it is Fuse 20 that has blown twice
     
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  24. Drae

    Drae Rookie

    Jul 3, 2016
    25
    And next week, they will be checking this out. Will revert back when they report to me.
     
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  25. Qavion

    Qavion F1 World Champ
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    Thanks for the updates, Drae. Curiosity is killing me :D
     

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