Alternator Or Battery? Need Help

After checking the wiring, and getting the alternator and battery checked, I'd start looking for patterns for unusual drains.

I once chased a "charging problem" for over a month on my '87 GT 'vert. It eventually ended up being a short in the A/C clutch coil. Being a convertible, the A/C didn't get used much, but when it was, it would drain the battery with the engine running in under an hour. I honestly didn't see the correlation between running the A/C and the battery going dead at the time. I finally figured it out because I had the defroster on while doing a charging test with an old ARBST "Bear" test machine (I miss those things), and when the A/C compressor cycled on, it went from reading 13 volts and positive amperage to 8 volts and negative amperage.

I also tracked down a slow drain in an old Chevy pickup to a horn relay that was staying energized. The contacts in the steering column were making contact, but the owner of the truck had long ago put aftermarket horns in with their own switch and disconnected the original horns. The relay was drawing just enough to run the battery down to the point of making it very sluggish to start since the truck was only driven about once a week.

Should you rule out the alternator itself, the wiring, and the battery, it's time to start looking at the rest of your electrical components.