328 Battery Drawdown | FerrariChat

328 Battery Drawdown

Discussion in 'Technical Q&A' started by qbert, Aug 30, 2020.

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  1. qbert

    qbert Rookie

    Mar 24, 2012
    7
    Full Name:
    Bob Head
    My 1989 328 GTS, with a brand new battery, will not start after sitting in the garage overnight. I placed an ammeter in series with the negative terminal and find I have a parasitic draw of 3.25 amps with the key off. My next step was to remove and replace each of the fuses, one at a time, and found the draw unaffected at 3.25 amps. The next step was to remove and replace each of the relays, with the same result. I next removed the smaller two cables (which I believe are routed to the fuse and relay board) of the three cables bolted to the positive battery clamp, and still saw a draw of 3.25 amps. This indicates to me that the problem lies somewhere in the larger cable (~1/2” diameter) of the three cables on the positive battery terminal. All of the lights, instruments, and accessories are working properly. At this point, I am at a loss. Has anyone experienced something similar?
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Aug 30, 2020
    Last edited: Aug 30, 2020
    Most likely something in the alternator electrics is the trouble (as the alternator and the starter motor are the only things that you haven't unplugged). The alternator warning light is designed to only detect a broken alternator belt, but it may misbehave when something goes haywire inside the alternator (but it may not, too). If it is not operating correctly ("on" with the key "on" and engine not running, and "off" when the engine is running) = that's a sure sign that something inside the alternator is bad. If the alternator warning light is still working correctly, you are then left with removing the large positive cable from the back of the alternator (or starter) and redoing your test. (Your 328 wiring diagram shows there is a(n engine bay?) connector in the large positive cable going to the alternator, but don't know its exact location or if getting to it would be easier or harder than getting to the back of the alternator - perhaps one of the 328ers can post a photo of it.)
     
  3. qbert

    qbert Rookie

    Mar 24, 2012
    7
    Full Name:
    Bob Head
    Thank you Steve. I was coming to the same conclusion that I have an alternator problem. I checked the red "battery" light on the dash, and it is not "on" with the key "on" and engine not running. Like you, I noticed in the wiring diagram that there is a connector on the positive cable, so I will look for it tomorrow. I'll update you when I am able to disconnect the positive cable.
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Unfortunately, that pretty much condemns you to an alternator-ectomy (but still do the test if you can)...:(
     
  5. qbert

    qbert Rookie

    Mar 24, 2012
    7
    Full Name:
    Bob Head
    Update: While laying on my back under the car, I was unable to disconnect any of the cables leading to the starter or alternator in attempt to isolate the current draw. As a result, I scheduled an appointment to take the car into my mechanic tomorrow morning to address the 3.25 amp parasitic draw. However, before doing so, we decided to do a Ferrari event today, which included a 165 mile drive. At the end of the drive, I rechecked the battery draw and find it now to be only 20 milliamps. I have no idea what's going on. Could the draw be associated with the ABS system? I'm still taking the car in tomorrow to discuss with the mechanic. I will continue to update this thread until the bitter end.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    And is your alternator warning light now working correctly, too?
     
  7. qbert

    qbert Rookie

    Mar 24, 2012
    7
    Full Name:
    Bob Head
    I just checked the warning light and it is working correctly. I did a cold start, ran the car for 30 seconds, shut it off, and rechecked the draw. It is still at 20 milliamps. When I turned the key off, the ABS warning light stayed on for about 15 seconds, and I noticed a buzzing sound from somewhere around the battery/brake reservoir area. I recall this happens frequently lately.
     
  8. POLO35

    POLO35 Formula Junior

    Feb 21, 2005
    712
    Treasure Coast Florida
    Full Name:
    MATT
    FYI you can jack up the right rear of car remove the
    wheel and fender well liner and your alternator will be right there very very easy access
     
  9. POLO35

    POLO35 Formula Junior

    Feb 21, 2005
    712
    Treasure Coast Florida
    Full Name:
    MATT
    Another thing to check you may not be aware but does your car have an aftermarket installed alarm system even when off and unarmed at Driveit draws amperag....mine had an old Clifford from the 80s between that and the analog clock what a lot which is another thing check your analog clock it could be malfunctioning
     
  10. qbert

    qbert Rookie

    Mar 24, 2012
    7
    Full Name:
    Bob Head
    Final update: Steve, you were correct. My mechanic removed the alternator and did a complete overhaul, including new bearings. The bench test showed the alternator output was insufficient to maintain the battery, even with all accessories off. After the rebuild, even the power windows operate faster. The parasitic draw is now zero with the clock and radio fuses pulled (20 milliamps with the clock and radio fuses in). In response to Formula Junior, my car is completely stock, except for the Kenwood radio, which has a small draw even when off. By the way, my car has 37,000 miles, and the R&I and alternator rebuild was approximately $1000, money well spent. Thanks to everyone for their support and thoughtful posts.
     

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