Charging system trouble?

Anonymous-0 · Mar 20, 2009

On my 931B Cat, it seems like the charging system isn't working properly but sometimes it does. It sat out all winter and I went out on a warmer day and it started right up. The next day I had to boost it. I had the alternator rebuilt last year and the guy said it was just normal wear that caused it to stop charging. I also put a new ammeter on that I don't think was needed. I did put a good quality one on. I have noticed that the ammeter needle will jump around on the + side but not always. After the machine has run for a while the ammeter needle stays in one place showing a slight charge. When the old alternator worked, the ammeter would show a high charge at first and then come down to a normal charge after about a minute. It has a one wire alternator and I think the regulator is built in. I think it's a Nippon Denso alternator. Does someone have an idea what's wrong? I'm wondering if I should take the alternator back to see if it has some minor problem or if it's something else. Thanks in advance. Dave

Farmerford · Mar 20, 2009

My D3B has always (the past 9 years) acted like your new alternator: even when the battery is low it doesn't move the needle much. If the battery is not low, it charges a few minutes at a higher rate (but not very high) and then settles down to a very low charge. I thought that was normal since these machines use no electricity once started, so if the battery starts fully charged, and the engine starts easily, it doesn't take much to bring it back to full charge.

Anonymous-0 · Mar 20, 2009

Dave, I thinkthere is a big bayonet pin plug in the main harness at the dash. Might have a poor connection there.
Later Bob

Anonymous-0 · Mar 20, 2009

There is a big plug that goes together right by the air filter hose on the back of the dash. It didn't fit together real tight, so I'll try and play with it a bit. I looked in the archives and someone mentioned the oil pressure switch shutting off power. I put a new one on but not the expensive OEM one. I used a Cole Hersey that was less than half the price. The hour meter works when it's running. I think I'll go ask the guy that did my alternator as well. He seems to know what he's doing and does a lot of older stuff nobody else wants to do. Thanks. Dave

Anonymous-0 · Mar 21, 2009

I talked to the alternator rebuilder. He said it will do that if the battery isn't fully charged. He also said it could be hard on the alternator and it would be a good idea to put a battery charger on to fully charge the battery. I would have thought the alt. would fully charge the battery after running for a few hours but I guess not. Dave

Charging system trouble?

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