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355 total electrical failure

Discussion in '348/355' started by Red_SLR, Jul 18, 2021.

  1. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
    42
    Full Name:
    Simon
    Took my car out for a very quick run today, 1 mile each way.

    On the way back about 100m from home the car died, revs dropped - dash blank and all electrical dead.
    Coasted to a stop and tried to restart but was dead. Ignition on the speedo would raise up to about 30mph and then slowly drop back to its stop. Weird.

    Turned the power cut off to off and waited a few min and tried again but dead still. Tried to push it but stuck in gear... sigh. Hazards not working... perfect!

    So had to get someone with jump cables out and we put power to it and everything came alive.

    Now in N we decided to push it home rather than risk jump starting it.

    So, what do we think? Dead battery? I have not changed it and had the car 5 years and I suspect its going to be a few years older than that again so my first thought is battery?

    My volt meter is in work so will have to wait till tomorrow for some diagnostics.

    The car normally lives on a ctek but had just come back after a repair to the seat potentiometer and I planned to take the car out so its been off the ctek the last 4-5 days.

    Or alternator? I guess if that was not working it would not be charging the battery... again need a volt meter to confirm... hm. Are the alternators fairly reliable on these cars?
     
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  3. spaghetti_jet

    spaghetti_jet Formula Junior

    Jan 5, 2005
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    Bob
    If it all powered up when you connected the jump leads then my money would be on a failed battery.

    It’s at least 5 years old, so worth changing anyway. Then you can start the car and check the alternator is charging with a voltmeter.
     
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  4. Kokose7en

    Kokose7en Karting
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    Dec 5, 2019
    157
    SF Bay Area
    alternator. Most likely what happened is that the battery had enough power to start the car and run. During your drive, there was no alternator output and the battery was supporting all electrical loads until it dropped under the lowest possible running voltage, maybe around 9v before the car died. A voltmeter will be good to have to test the static voltage of the battery and alternator output voltage. In your case. I would charge the battery up before testing the alternator as it will put a large load on the alternator if you just jump start it with a dead battery.
     
  5. phrogs

    phrogs F1 Veteran
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    Apr 13, 2004
    6,651
    Michigan sometimes out west chasing fires
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    Johnny
    Hard to say without testing, then charging that battery to eliminate it.

    Then go from there.
     
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  6. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
    42
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    Simon
    Found an old volt meter and its metering out at 2.5v in the engine bay. I reckon failed cell in the battery then? If it was the alternator then I would have expected 10v ish now its had chance to sit there?

    Plan now is get the battery off tomorrow night and then get it tested on Tuesday. Is there a good battery to replace with? I am going to guess its due anyway but will see if I can see a date code.

    I wonder if keeping it on the ctek has been hiding the issue? Then as its been off the ctek this week its finally given up?

    If it is the alternator (I need to check the belt is still there!) is that a DIY job or better to take it in?
     
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  8. spaghetti_jet

    spaghetti_jet Formula Junior

    Jan 5, 2005
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    Bob
    Definitely change the battery if it’s more than 5 years old. The last two batteries I’ve had to change on my other cars just failed without warning at around that time. In the “old days” batteries would let you know they were on their way out by losing charge, or being sluggish in cold weather and you could nurse them along for a while. That doesn’t seem to be the case anymore. The last one I changed started my wife’s car perfectly, she took the kids to school, came home, no issue. Parked the car for a couple of hours, went to start and nothing! I left it on charge overnight, it had good voltage, but would not produce the current to crank the engine. It may be that yours has developed a similar fault.

    As for the alternator, it is “do-able” from underneath, but fiddly to get out. Many of us have rebuilt with new rectifier & regulator. You can find interchange parts to rebuild but entire new alternators are pricey if you find one.

    Another thing to check is whether the wires are frayed coming out of the alternator connector plug into the loom. Vibration and heat can break the wires inside but leave the insulation looking intact creating an open circuit and affecting the charging.

    But if you didn’t have the battery light on while you were driving (before the breakdown) then your alternator is probably ok.

    Good luck with it & let us know how you go.
     
  9. emac

    emac Formula Junior
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    Sep 14, 2014
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    ernest
    I have several cars that stay on tenders and rarely get used. What I have found is that the batteries do last a lot longer, but when they die it usually happens after you start it and it can be very hard on the alternator. I think it cooked the alternator in my NSX. If the battery is past its expiration date and the car has lots of electronics, I would replace it.

    Sounds like you need to replace the battery and check the alternator.
     
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  10. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
    42
    Full Name:
    Simon
    Battery is out. Mmmm that was a fun job I have changed a LOT of batteries over the years (at least 4 or 5 a year at work) and thats probably one of the worst for access, thanks ferrari. FFS.

    Anyway, I have changed a lot like I say so my commentators eye is that battery is at least 10 years old. I cant see a date code but will have a closer look tomorrow. Its metering out at 11.9v now. No doubt thats going to drop a lot with a bit of load - will try tomorrow with something.

    Its a Varta Silver which IME are pretty decent.
     
  11. emac

    emac Formula Junior
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    11.9 = dead
     
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  13. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
    42
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    Simon
    Yeah.

    Its a 417 date code so Jan 2014 production. 7.5 years is not bad I guess.
     
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  14. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
    42
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    Simon
    OK so new problem.

    New battery fitted - went for the same Varta E38 so fits fine. Fires up on the button.... but only seeing 12.4v... so alternator not charging.

    Let it run for a few seconds and the battery light comes on... dang.

    Someone tell me there is a fuse for the alternator.... :(
     
  15. spaghetti_jet

    spaghetti_jet Formula Junior

    Jan 5, 2005
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    #12 spaghetti_jet, Jul 20, 2021
    Last edited: Jul 20, 2021
    What voltage do you get when the engine is running? If the alternator is charging then it should be in the range of around 13.5 to 14.5 volts.

    if not, then the alternator isn’t charging - before you do anything else, “jiggle” the wires coming out of the back of the round 3-way connector on the back of the alternator (ideally, while it’s running but please be safe) and see if it starts charging (I know at least 2 355’s that had frayed wire problem) If it does then you have frayed wires, or a bad connector otherwise it’s alternator out time. You can find several posts about alternator removal & rebuild on here.

    when it’s out you should check the wiring and rebuild the alternator with a new diode pack, regulator and brushes. Look at the bearings, too. The grease had turned to wax in mine.
     
  16. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
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    Simon
    Engine running 12.4 and it dropped to 12.3 after 20-30 seconds and at that point I looked in the cabin and saw the battery light was on.

    I checked the 3 black wires in the engine bay they are tight and look ok.

    I think I will have to jack it up and get under and have a look at it - job for the weekend I suspect.
     
  17. spaghetti_jet

    spaghetti_jet Formula Junior

    Jan 5, 2005
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    Bob
    so, definitely not charging.

    the three thick black cables in the engine compartment is the connector block with one cable that comes from the battery, then one goes to the starter and the other to the alternator.

    the three wires I’m talking about are much thinner and come directly out of the back of the alternator. They are just under the exhaust manifold and have a tough life!

    on the plus side — the engine runs and there are worse things that can happen o_O
     
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  18. emac

    emac Formula Junior
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    ernest
    Sounds like the dead battery took out the alternator. Same thing on my NSX, I replaced the VR and diode pack and all was back to normal.
     
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  19. spaghetti_jet

    spaghetti_jet Formula Junior

    Jan 5, 2005
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    That’s my bet too.
     
  20. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
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    Simon
    Thanks guys I will have a look at it and decide if I will DIY.. I really should just get a lift in my garage LOL
     
  21. Qavion

    Qavion F1 Veteran
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    Feb 20, 2015
    5,658
    Sydney
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    Ian Riddell
    The three pin plug on the alternator should have the following wires:

    Disconnect the three pin plug on the alternator and check for the following (car side of the plug, not the alternator side):

    red: Sense wire... check for battery power on this wire (car not running)
    yellow: Ignition wire... check for ignition key power (car not running, ignition on)
    yellow/green: Battery warning light wire... possibly ok since your light is on. I'm just wondering if the warning light goes out if you short out this wire to the yellow wire.

    Image Unavailable, Please Login
    If these wires check out ok, then the alternator itself will be probably be faulty.
     
  22. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    8,886
    New England/FL
    Might be useful:

    Alternator diode/regular

    Get the USI regulator,
    Part number:
    71-30003/SCP

    See PDF file Denso Regulator
    Denso part # = 126000-400
     

    Attached Files:

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  23. Red_SLR

    Red_SLR Rookie

    Jul 22, 2019
    42
    Full Name:
    Simon
    Thanks guys I have ordered a refurbished alternator the one on the car looks factory to me so I suspect its that - even if its not given I have now changed the battery its probably a good idea to remove the alternator. My local indy has quoted a very reasonable price to fit it so as soon as it arrives I will have it done and report back. I will then probably send out the old factory alternator to a local place to be repaired once I have the bits to do it and keep it as a spare.
     
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