Charging system over charging?

I put a rebuilt alternator and new voltage regulator on my skid steer with a Kubota diesel. I also put new batteries in. Lots of problems getting a voltage regulator to work right. Eventually took to the place that rebuilt the alt. and they said they just hooked up a regulator and it worked. The dash light stayed on so they took one wire off and said it's OK. At the time(about 3 months ago) it was putting out close to 15 volts which they said was OK cause the battery might have been low. The alternator also got pretty hot. I've only used the machine a few hours since then but had to bring it to the city for snow removal. It started right up and the charging light went off. I had it running for about 35 minutes while I hooked up the trailer etc. I noticed a smell of battery acid and checked the output voltage. It was 16.78! I put the machine on the trailer and brought it home. I checked again and when first started, the voltage was around 13.4 and slowly went up close to 17 again. The battery's had lost some fluid as well. I spent over $250 for the alt., regulator and to have them hook up a regulator that they said was fine. Plus I bought 2 new batteries. I had a bigger style regulator that lasted over 10 years and this machine was known for regulator issues. They say the larger style regulators aren't available but won't phone the supplier. I'm taking the machine there Monday. Anybody have an idea what's wrong? It's a 25 amp Nippon Denso alternator with external regulator. Could something in the alt. be bad? It's very frustrating. Dave

Sure sounds like you've got a problem. I'd take the thing back to your rebuilder and feed it to them.

Over voltage on an external regulator alternator can be caused by a poor ground between the alternator and regulator. The fact that it works correctly on the rebuilders test bench, but not on your loader points to a bad ground being the suspect.

Hook a temporary ground wire from the alternator case to the regulator ground (Most regulators ground through the mounting screws) and see if the voltage returns to a normal 13.5 -14.8 volts.

Can often be a broken or bad ground strap between the engine and loader chassis causing the poor regulator to alternator ground, if the regulator is not mounted to the alternator or engine, but on the loader chassis.
If the temp ground wire fixes the problem, it may pay to make it a permanent addition.
Depending on a ground between rusty greasy bolted together parts often leads to problems like this.

If it's got an external reg I'd say you have a wiring problem between the alt and reg. Either the ground is bad or the sense line is bad and it's not sensing the correct voltage.

Rod

Thanks. I'll try the extra ground wire from the alt. to the regulator. Dave

Alternator regulators work by either grounding the field or supplying voltage to the field. The first thing I'd do is confirm that the alternator doesn't charge when the field wire is removed. If it continues to charge with the field wire open, you've got an internal short in the alternator. Otherwise it must be a problem with the regulator or wiring.

Hello 135 Fan,
The voltage is way to high.
Normal charginr voltage is between 13.8 and 14.2 volts. It may at times be abit higher but anything about 14.5 V it is a overcharging condition. Amperage at any given voltage is also important. If you charging 1 amp or less at 16 volts, you won't hurt the battery, but it should not be that high.
Why not go to a single wire alternator?. It will have a built in regulator too. Besides being a easy set up, and a higher output capacity, it will probably be cheaper.
Guido.

That would have been a solution except I had the alternator rebuilt when I discovered a charging problem. I just took the alt. in to have it checked. They said the brushes didn't even make contact so I had it rebuilt.($130) Then I tried a half a dozen voltage regulators($65) and couldn't get it to work right so I took the whole machine in and was charged another $100 and the one guy said he just hooked up a regulator and it worked. I noticed a light stayed on and they said one wire on the alt. wasn't needed with that reg., so took it off and taped it. At first it seemed OK but I've only used the machine about 3 or 4 hours and it's just sat for about 3 months. I smelled the battery acid and discovered the overcharging problem. Dave

Hello 135 Fan,
It is a regulating problem. The regulator has to have a good groung to work properly.The alternator is doing its job.
Its not an easy thing to pinpoint, doing it long distance its even harder.
Hope you get enough info to get it done.
Its really aggravating, when all is new and does not work properly.
Good Luck..............Guido.