Alternator slightly high output?

[scenarioL113]

One of my alternators is reading about 14.9 to 15.2 volts when charging.

I pulled the alternator and brought it to the local shop (old school shop) and they bench tested and under load and it never went over 14.5 volts. I swapped the alternators from port engine to starboard engine and the problem followed the alternator.

With that said I know the grounds and bonds are all good and all the connections are good as well. I am pretty meticulous on the electrical side.

I used a digital multimeter and checked at the battery terminals and also checked it at the charging post on back of the alternator and got the same results.

The old stewart warner gauges at the helm pretty much follow what the multi-meter is reading (maybe just slightly lower)

I guess I am wondering if my readings are just not totally accurate and should I leave it alone???

15volts might be a bit over for charging but not radically too much???

I dont know, any input is appreciated...

[Tony Meola]

Are you sure your meter is not off?

[Carl]

Electrical has never been MY strongpoint…not even my weak point.

But after I would fiddle, switch this, check that and that My friend would ask if I’d say uncle and let him have a crack at it. Reluctantly I’d move away and more times than not he found a bad ground and magically my problem disappeared.

With that in mind, Hearing the problem travels with the alternator I’d be looking at lines that are not independent of each motor. Common ground connections to the batteries, motors.
Battery switch connections. Grounds to the panels.

If not obvious, I’m only guessing like I’d do on my boat, car, machines.

[Ironworker]

As the old saying goes, One wire hook it up. Two wires ###### it up. Three wires blow it up!

It sounds like your voltage regulator may be slightly off. At 14.9 volts, I wouldn't worry about it.

[Carl]

I think the regulators are internal on the Cummins alternators and it was bench tested checking out fine.

[Tony Meola]

I think the regulators are internal on the Cummins alternators and it was bench tested checking out fine.

That is why I said to check the volt meter.

Not sure how a bad ground would cause it to charge higher. If anything a bad ground would make it not charge. Something is definetly off, especially if it bench tested good.

[scenarioL113]

I will check with a second digital multi-meter. The alternator at the shop bench-tested at 14.5 volts.

14.9 -15.2 was via my multi-meter at the battery and also at the post on rear of the alternator but like Tony said earlier my multi-meter could be wrong and I need to check with a second one.

If the output is under 15 volts I will leave it alone but at 15 or above I am worried about cooking a $300 battery.

Since I switched the alternators to the opposite engine the one in question is now only charging the single starboard battery and not charging the house battery