Alternator capacity | Page 2 | FerrariChat

Alternator capacity

Discussion in '365 GT4 2+2/400/412' started by SouthJersey400i, Jul 26, 2015.

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  1. samsaprunoff

    samsaprunoff F1 Rookie
    Silver Subscribed

    Jun 8, 2004
    4,160
    Edmonton, AB Canada
    Full Name:
    Sam Saprunoff
    Good day Armen,

    Before I would assume that your alternator is under capacity, I would investigate the issue further. For example your comment about the battery voltage being 14-15V when cold and when the fans kick in (engine warm) the voltage drops to 12V... with the cooling fans only drawing 2.5-3A means that something else or other items are drawing a lot of current. In other words 2.5/3A is not that much of a load to cause that much of a voltage drop. Have you performed a load test on your battery? The battery is actually a very important part of your electrical and charging system. As an example on some cases a disconnected battery when a car is running can cause damage to the alternator/regulator, etc. As I said, I would investigate where or what are the large loads that seem to be sucking the energy away from your Alternator. Putting a larger output Alternator may be masking some other underlying issues that may cause a lot of problems later.

    Cheers,

    Sam
     
  2. Ak Jim

    Ak Jim F1 Veteran
    Owner Rossa Subscribed

    Dec 23, 2007
    8,450
    North Pole AK
    I had some charging issues on hot days with the AC on. I took the alternator off the car and had it tested. The shop said it was good but I would still occasionally have low voltage on hot days with the AC on. One day the alternator quit working so I sent it and the voltage regulator off to be rebuilt. Interestingly enough even though in the past the alternator was tested to be ok it worked much better after being rebuilt.
     
  3. miami355

    miami355 Karting

    Sep 2, 2006
    136
    Miami, FL
    I was quoted $260 for the alternator upgrade. Well worth the insurance to know the "guts" are new and improved. I'm going to do both alternators. For me, the $500 is worth preventing a ruined night out with a dead battery.

    David
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,035
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #29 Steve Magnusson, Mar 28, 2018
    Last edited: Mar 28, 2018
    Section 6 in your OM indicates the alternator is a "Marelli GCA 113A", and an internet search on that gives this thread from Tom Yang's site that says it's rated at 55A (which doesn't seem unreasonable for a carb car without a lot of electrics/electronics from the 1970's):

    http://www.tomyang.net/cars/phpBB3/viewtopic.php?t=2801

    If just the cooling fans coming "on" leads to failure, there has to be a problem - the headlights would draw a lot more current. What happens if you turn the highbeam headlights "on" at warm idle with the cooling fans "on"?
     
  5. ag512bbi

    ag512bbi F1 Veteran
    Owner Silver Subscribed

    Nov 8, 2003
    7,540
    So. Cal
    Full Name:
    Armen
    I'm picking up the Alternator tomorrow from a place in Monrovia, CA.
    I will update what was completed.
     
  6. miami355

    miami355 Karting

    Sep 2, 2006
    136
    Miami, FL
    Sorry to revive an old thread, but was it hard to change
    Sorry to revive an old thread, but I'm looking to upgrade my alternator and battery wiring. Was it difficult? You did the main battery cables and the alternator?
     
  7. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,591
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    I have some new news. With my one uprated alternator, I still had a dead battery in June after a 4 hour drive with AC, lights and wipers. I had battery tested and it was not too old but if showed less than max amps. Battery has been replaced and I did a long weekend run this past weekend with A/C but without lights and wipers. All was fine. I am confident It will handle most any trip now.

    In an earlier post above Part Time told me where the alternator wires arrive behind battery and below wipers. It took a little hunting but Voila! They are in a cute little plastic box under the wipers, I think between the air filter pivot (400i). Wires looked in good condition and i cleaned contacts that were also quite clean; the little box protects contacts from weather and engine.

    I think my rewiring of fans (like I did with fuel pumps) has increased the speed and therefore the current to my fans. On this last trip, I was surprised the water and oil temp ran 5-10 degrees cooler than similar conditions in the past; Long Island's North Fork is known for bumper to bumper traffic this time of year. Higher voltage to DC motors will mean higher current and speed unlike a synchronous AC motor.

    Ken
     
  8. Part Time

    Part Time Formula Junior
    Silver Subscribed

    Dec 16, 2013
    494
    Port St. Lucie, Fl
    Full Name:
    Gary Shore
    Thanks ! Happy to be of help, half of everything I know about these cars I gained from this forum.

    Gary
     
  9. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,591
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    I have some new news. With my one uprated alternator, I still had a dead battery in June after a 4 hour drive with AC, lights and wipers. I had battery tested and it was not too old but if showed less than max amps. Battery has been replaced and did a long weekend run this past weekend with A/C ut without lights and wipers. All was fine

    In an earlier post above
     
  10. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,591
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    I usually hookup by battery trickle charger in the first few days after a trip. I did not this past week and when I started the car, I got the first little "chirp" from one of the belts; I am sure it was the upgraded alternator's belt. Chirp lasted a second at most. I'm still confident the small width belts will work for an 80 Amp alternator; I would not go for the 145 A option!
    Ken
     

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