Forums/Z31P/z31-repairs-forums electronics/Possible bad alternator
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ty86300zxt: (2023-11-01 23:38:58)
Recently replaced my 86 Turbo Alternator with an AC Delco remanufactured Alternator. It has been running fine for a ew months but this past weekend came out to a totally flat / dead battery. had driven it probably 24 hours before hand and it had started and drove fine. Next day when i went to drive it was totally dead. Took the battery and put it on a charger and now when i've put it back in the car and connected i'm getting the Charge warning lamp on when the CAR is off. Car starts and drives fine and when the car is running the Charge Warning lamp is off as it should be and seems to be charging the battery fine. but as soon as the car is turned off the charge warning light comes on and stays on - which of course will drain the battery pretty quickly.
Am i right to assume that there is an internal short in the alternator that is most likely providing power to the charge light when the car is off?
Z_Karma: (2023-11-02 18:53:09)
You'll probably have to do something called a parasitic drain test to determine what is causing the drain. Usually this involves removing fuses until the current draw drops, but i would see if it drops when you unplug the alternator plug. I've had parasitic drains from the anti theft system, but never had a alternator be the cause.
mwolvinm: (2023-11-03 01:00:18)
That charge warning light should be on when the car is off. If the engine isn’t running, it’s not going to charge. I suggest taking the car to the parts store and doing a full electrical test. They can test the battery and alternator for free. I wouldn’t be surprised if the battery has a bad cell. Other possible causes is a loose/dirty ground or loose connection at the battery.
mwolvinm: (2023-11-06 00:56:19)
Yeah…. You have a short somewhere
badq45t: (2023-12-04 21:25:45)
I had something similar happen years ago, it turned out that the battery cables were bad. The mechanic put in a new set of cables and that solved it. I do not know about quality of AC Delco didn't know they made Nissan parts but that should be OEM level quality so that shouldn't be failing so quickly. If you have original battery cables they are too old anyways and replace those for sure. As also stated my alarm was for sure causing drains and pulled that fuse years ago.
FlyingT: (2023-12-06 23:18:31)
With car shut off, get a digital meter, set it up for checking current amperage, remove a fuse, and touch the meter leads across the 2 fuse contacts in the fuse box. It should tell you the current running thru that circuit. Put the fuse back in. Do that for each fuse and you should find the circuit with the high parasitic losses. Some losses are normal, like the clock and alarm systems.
Also, while the car is off, check the battery voltage. It should be 12+ volts if fully charged. Start the car and retest the voltage at the battery and it should be close to 14V. That tells you the alternator is working fine and charging the battery.