Charging problem

Sat Apr 24, 2010 5:43 am

I'm working on an SA that has been converted to 12v one wire alternator. The battery goes dead after a few starts. After an overnight charge at 14.2 the battery will hold at about 13.6. When the engine is running the ammeter shows discharge. A check with my multimeter confirmed the ammeter was wired backward. The alternator is putting out fine. Here's the problem. With the engine running the volt meter jumps all over the place, so fast you can't read it. The only thing I can find wrong is the reversed ammeter. Could this be the problem with the voltmeter? I checked every hot spot on the tractor that I could get to with the same result.

Re: Charging problem

Sat Apr 24, 2010 5:46 am

Dan - the ammeter being wired backward would not cause that. I would bet that the alternator has some shorted diodes in it.

Re: Charging problem

Mon Apr 26, 2010 5:24 am

Problem fixed. The only thing I did was reverse the ammeter and everything is working properly. I still don't know why but I'm not going to question the results. :D

Re: Charging problem

Mon Apr 26, 2010 7:44 am

The voltmeter, mounted on the tractor and connected to the tractor wiring or is the voltmeter a test instrument used momentarily to verify the voltage? A voltmeter connected to the tractor wiring draws a small current which can discharge the battery over time. Voltmeters should be wired so as to be powered only when the ignition switch is on.

Re: Charging problem

Tue Apr 27, 2010 5:02 am

It's a Sperry digital multimeter.

Re: Charging problem

Tue Apr 27, 2010 11:08 am

Dan - I would bet that one of the connections to the ammeter was not a good solid connection. When you reversed the leads you must have made better connections than what you had before. Digital voltmeters are really sensitive on these types of circuits.

Re: Charging problem

Wed Apr 28, 2010 6:03 am

I think that is exactly what happened. Never to old to learn. Thanks BD.