battery problem

[wambus]

New problem with my ride. I installed a used battery that had a full charge. It has been working fine for over a month. Now, suddenly, the battery does not have enough charge to turn over the motor - all other stuff works. When driving, the guage indicates about 14v being put out by the alternator. I am forced to pull off the negative terminal each time I stop in order to start up again. I had to replace the last battery because the brake light switch failed; the car was not being driven so this was not noticed until the old battery was stone cold dead. Any common problems to look for in this regard?

[Jeeves]

I've never had this problem, but I believe the alternator has a diode or a diode pack that can fail. This will cause the battery to unload back into the alternator when the car is off, thus killing the battery. A warm alternator hours after the car is off is a good indicator of this (as it should generate a decent amount of heat)

[wambus]

If I have the battery on a charger and also still connected up to the cars's cables, will that current flow back to the alternator and warm it up? Other than that test, how can I tell if this is the problem?

[Jeeves]

Take it (or the car) to an autozone, or a checker or something of the sort. Most of those places can test alternators.