[Heliarc]

I'm assuming you tested it with a voltmeter at the battery terminals while the engine was running.If it holds 12.5 it should be ok to go though that is a low reading.It should be up around 15 volts when it's running.You might have to get it up on stands and run it with the back wheels up to get a good reading on it.The way mine is wired, it will idle without holding the pedal.At idle it only puts out about 12 volts.When the engine is at speed though the reading climbs to about 15 volts.

One test you could do is disconnect a battery terminal while the engine is running.However I'm not sure about what it may do to other components on the cart.I test car alternators this way.If the engine dies when the battery terminal is disconnected, then you aren't charging.However, jacking it up, and getting the engine to speed, the testing with a voltmeter at the battery terminals should be a good enough, and safer test.

Another test would be to remove your alternator and take it to an auto parts shop.Most shops can bench test your alternator.If your alternator checks out ok, you can look at your connections, and your regulator.They might be able to test that as well.

Now, what could be wrong.This could actually be a few things.You could have some corrosion buildup on your battery terminals.This will prevent it from charging the battery.It would crank slow as well since the battery isn't getting much of a charge, or it might not crank at all unless you jump start it.But once started it would probably run fine.

A bad voltage regulator will prevent you from charging as well and will make it seem like your alternator is dead.This is a much cheaper fix than an alternator.

Hope this helps.If not, put up what kind of cart you're working with and the symptoms you experience.This shouldn't be a terrible issue to solve.