Dead battery - Is the alternator bad?

[3point2]

Helpful posts! Thanks!

I just checked voltage with the car off and it's at 12.2V. With the car on, it's 14.3V. So does that mean the alternator is good?

I'm starting to suspect that something is draining the battery from somewhere. When I was driving the car the last time, the radio went out. Now with the battery charged up it works fine. When the car sat for a few days, the battery was completely dead.

Any other thoughts?

If it was the voltage regulator, the voltage would be showing up all over the place on the multimeter with the car on, right? It holds a steady 14.2-14.3V with the car on.