Volt Meter reading 16 V @ 1000rpm (Out of gear)

At idle (out of gear) my volt meter fluctuates between 8 and 12 volts. When I run up
to 1000 rpm, it pegs at 16 volts. I think it's a regulator problem and I'm pulling the alternator to have it checked out. My question is: How much damage, if any, have I done to my 3-8D AGMs? (The alternator gets as hot as a pistol.)

You are probably ok, of course depending on how long that has been going on.
Many regulators and chargers have equalize functions that push the voltage up that high or near to it. Some AGM mfgrs. suggest that an equalize is ok and should be done.

The biggest problem would be if the high voltage went on long enough that the battery would be forced to outgas popping the vents. If you don't see any signs at the vents of residue or moisture then you are likely ok.

In most cases, in my understanding, that condition would have to go on for a few hours continuously.

It's good you caught it and hopefully early.

Change the voltage regulator if its an auto "one wire" have it rebuilt with out the internal regulator , just lead the field wire lead out , and buy an auto regulator if charge times don't matter ,

or a 3 or 4 stage regulator if charge times do matter.

16 volts is near equalizaton voltage and will fry the batteries if pumped into them over extended periods.* Alternators get hot, period, so that by itself doesn't mean a whole lot.* FF is correct, if the regulator is just what is built in the alternator, it isn't really designed to deal with deep cycle AGM batteries.* The best way to kill an AGM is to overheat it, so this is definitely something to fix.* Were it me, I'd spring for a 3 stage external regulator that is programmable for AGM requirements, which are pretty specific.

FF is correct, if the regulator is just what is built in the alternator, it isn't really designed to deal with deep cycle AGM batteries

It isn't designed to recharge a large house bank of wet batts either.

The auto/truck style V reg is good at keeping a 98% charged batt going and the lights and fans on.

Period.

Did you ever check the voltage with an external Volmeter?
A bad connection could make your panel voltmeter show false readings

R-R* yes, We checked the voltage with an external volt meter.

SeaHorse II wrote:

R-R* yes, We checked the voltage with an external volt meter.

If you are indeed getting 16 volts, you have a problem and don't want to continue running with this issue. Pull the alternator and take it to the shop for testing as you indicated. Have the batteries tested by any local battery shop. Then you will know for sure. Chuck

Click to expand...

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-- Edited by Capn Chuck on Tuesday 7th of December 2010 09:47:24 AM

Capn Chuck wrote:If you are indeed getting 16 volts, you have a problem and don't want to continue running with this issue....

Click to expand...

Alternator has been pulled & is in the shop and an external, three stage programmable regulator is being installed this week.

Thanks guys!

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The alternator has been rebuilt (new bearings, etc,) and a 3 stage external regulator installed & programmed for AGMs. (Balmar). Everything is working perfectly.
Thanks guys, I appreciate the feed back.

-- Edited by SeaHorse II on Saturday 11th of December 2010 04:55:40 PM