New battery is dead

I have been fighting a battery issue for awhile now on my 01 GT. Originally I had a 4 year old never start that died because of age I am sure. I had bought a wrecked car from a auction that had a less than a year old napa legend battery in it that was dead. I took it to napa and they gave me a brand new napa legend battery that I put in my GT. Anyway that battery worked great for a couple of months. Then it got to where if my car sat for a couple of days it had to be jumped. Now if it sits overnight it needs to be jumped. I tested my alternator with my multimeter and it says it is charging 13.9 volts at idle and it falls off to 13.8 at around 1500 rpm's. From what I remember a alternator should charge over 14 volts at idle and increase as rpm's rise. Wondering if my memory is correct and if I should replace my alternator?

Hwystar1 said:

Do you still have the mach stereo system in it?

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No, It had been replaced with a aftermarket stereo before I bought the car. The security light is always flashing though. I don't think it draws enough to run the battery down though. The car had a never start battery when I bought it and it lasted 2 years

95Cobra302 said:

I would diagnose first before replacing. Do a load test first, while engine running turn on all your accessories, headlights, ac, fan, wipers, etc. and see where the volts go. They should drop some, but still should read above 12.8.

And remember at all the parts stores, they can come out to your car with a battery and load tester to check it for you if you don't have the equipment.

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I checked it with everything on and it was charging 13.8 volts