I Have A 1993 Mazda Mx3 And The Car Battery Keeps Dying But It's A New Alternato

Off the top of my head, if I were to start trying to find your problem I'd start this way, with the car turned off. Sorry for the long, complex crap, but I tried to simplify my thoughts as much as possible.

1: Read the voltage at the battery terminals with the battery connected. Take note of this number.
2: Disconnect the battery terminals.
3: Read the battery voltage. Should be at least 13 (13.5 is optimal).

At this point, if the voltage is different at all, something is drawing power from the battery, and is likely what is causing your issue. I'll get into that more later (since it will likely be the case), either way, proceed:

4: If the battery voltage is less than 13.5v, then charge the battery off the car (autozone or someplace similar will often do this for free if you don't have a charger) until the voltage is appropriate. If the battery won't charge to an appropriate level, then its shot. If it charges to an appropriate level but loses charge while disconnected from the car, it's shot. Take it back and get another. Once you have another battery, check the voltage, and stick it on the car and start over: the battery might have been your problem, but you still need to check for that voltage difference indicating a power draw, in case it's the REASON your battery went bad. Otherwise, once the battery is charged, stick it on the car and start over with a fully charged battery. You need to know if something in the car's wiring system is drawing power.

5: From here, there are 3 possible scenarios:
a:You discovered your (new) battery was bad, and replaced it, and confirmed that with a new, charged, battery, your car was running at an appropriate voltage.

b:You discovered that something in your car was drawing power from the battery even while off, and you need to find out what it is.

c:You didn't discover crap, because you made sure the battery was charged and then there didn't seem to be a difference.

If (b), there's either a dead short in your wiring system or something is running when it shouldn't.
If (c), there's either a dead short in your wiring system, or something is running when it shouldn't, or your new alternator isn't working right, and you're losing charge slowly. Take your car to AutoZone and have them test your alternator for free.

If it's not your alternator, and it's not your battery, then you need to begin the possibly long and painful process of troubleshooting your electronics.

If your car is drawing power ALL OF THE TIME (Option (b)), then remove fuses one at a time until the power draw stops (voltage returns to a normal level). If you can pinpoint the problem to a certain fuse/system, then you can proceed from there. If it never stops, the problem is before your fuseblock: probably a main battery cable rubbing the frame or something. Good luck!

If your car is NOT drawing power all of the time, and the alternator tested fine, then, good luck! You're tasked with the challenge of turning things on in the car until your voltage drops so you can figure out what's killing you.

No matter what you do, I would probably avoid that mechanic. Best case, he replaced your alternator with one that's already bad by accident. Worse case, he replaced an alternator that didn't need replacing because he couldn't be bothered to do a 5 minute test properly. Worst case, he did nothing and charged you for it.

Thanks

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Techygirl