(FINAL Update )...Alternator voltage too high, question

OK, there's lots to be said about dash voltmeters. But, normally all I use it for is on my panel scan as soon as I start the vehicle, and if I detect a change from normal I look into it. To me, in a vehicle that has only been driven by only one person (me) the accuracy is not as meaningful as detecting a departure from what I consider normal. This time, something is not normal. I only visit troublshooting electrical problems very infrequently. In this case, ONCE in 13 years. This is the second time. I'm calling for help from those who know what they're doing. Thanks

My voltage regulator in my engine computer would allow 14.9v, but the range it allowed was 13.7 to 14.9v

14.9 being too high and often it would choose 13.7 when battery was still far from fully charged had me bypass this voltage regulator and add an adjustable one with potentiometer on dashboard next to voltmeters whose voltage sense lines are right on battery terminals.

So I choose, and generally leave it at 14.4v until I know battery is fully charged or battery is above 87f, then I lower it

I understand the gauge reading different is a red flag to you. I'd double check the gauge. and the connections on back of alternator and firewall grounds.

And get a can of Caig Deoxit d5 spray for any connectors you open. no other electrical contact cleaner comes close. The presence of dielectric grease does not mean the conducting surfaces are 'just fine', as so many people seem to think.

I have feeling that about 40 percent of batteries are disposed still having lot of life in them, only because the "Oil change 3000 and battery replacement every 4 years" mentality takes 50 years to shake off.
Our family fleet had several batteries lasting 12-13 years, where one of the myths is that CA heat kill batteries prematurely.
I also hear about car batteries lasting 17 years and those are reliable reports.
Latest technology makes pocket-size digital battery testers that IMHO each RV owner should have. I still have old boxy load tester, so hold on spending money on new technology.
Than battery charging is whole science. Seems topping-off does harm them.
My 2-years old computer come with 4 different programs for charging (those are different types batteries, so not all principals are the same)
So the first choice of having batteries fully charged come with warning that it will shorten their life.
I choose longer battery life program, that will not start charging till batteries drop below 80 percent .
Comparing flooded batteries. Our Mercedes cars don't charge higher than 13.9V and those are that can run on the same battery for 12 years.
My Ford Trucks charge 14.2- 14.5V and it is hard to run the same battery for longer than 6 years.

Cloud Dancer wrote:
Mine is a 2003 Spartan chassis, 8.3 350HP Cummins engine, Leece Neville HD alternator with integral voltage regulator. It set at the lake for a month, hooked up to shore power, and I went to check it out, cranked right up, but but the dashboard voltmeter started showing 14.5 to 15 volts. I had never seen this before. I checked the 6 years old house batteries, one was weak, replaced all 4 (golf cart 6 volt). NO change. Tried it with shore power disconnected, no change.
Question: What's the best guess? Change the 2 chassis group 31 batteries, or is it the voltage regulator? Thanks

That is normal and GC-2's need 14.8 to properly charge anyways.

My alternator gauge never moves. Until it did two years ago and it was the alternator.
Doubt you have a battery issue.

My Ford Trucks charge 14.2- 14.5V and it is hard to run the same battery for longer than 6 years.

The conclusion you reached, that higher alternator voltage is responsible for lack of battery longevity, is not the same as the majority of automotive engineers designing 12 V systems.
The optimal charging situation is to recover from high starter draw and return the battery to a full SOC as quickly as possible.

FWIW, the original, slightly abused Motorcraft battery installed in my '03 Ford Superduty was replaced at 10 yrs., one month.

I'm sorry to hear that the OP discounts the information related before his last post. There are many members on the Forum that have rich technical experience. Maybe he's in search of a different answer?

However, I don't discount observation and if CD noticed an abnormality in his gauge readings, an investigation would be prudent. Since alternator output is proportional to battery acceptance, a tuneup of the battery and the connections would be my first step. I'd suggest to remove and clean all the connections to the battery, clean up the case, and charge the battery overnight at a small amperage charge. At the next start sequence, the gauge may read that the voltage is lower. That would indicate that the battery, in the previous observed abnormality, was slightly discharged more than normal and the alternator was operating correctly.

westend,
Are you referring to this post?
*
"Unless it's very hot out, the voltages your seeing are correct and normal. If you manage to lower them you won't be doing your batteries or anything else any favors."

Yes, it's been very hot. And, my motorhome has spent most of its life (13 years) in the sun belt, from Arizona to Georgia. I'm the only one who has driven it. I've jumped in it when the weather is HOT, and have started it many times, as you can imagine. I always check/monitor the instrument panel meters/gauges right after it starts. THIS is the first time the voltmeter has gone that high, and this is the first time is will NOT go down, at all, no matter how long I run it (within reason). Therefore, I simply have to find out the reason. I'm not going to do nothing, I gotta do something. Right now, I'm simply going to try to eliminate the possibility of the problem being a bad battery. Out of six, batteries, I've got 2 to go. Then, I'll report back. I feel I owe it to everyone to do at least that.
But, I've got to ask, what would you do? OK, I see what you would do. I've already cleaned all the cable-to-battery connections (many), and I've checked the battery voltage, separately with cables disconnected. These two batteries are a bit over 6 years old. That's about the interval that I've always changed the batteries, anyway. Why not now?

I wrote that the voltage will be a bit lower if it's very hot (especially if the battery is in the eng compartment) because they don't like higher voltage when they're hot.

I don't blame you for replacing batteries when they get older.
I've been driving for about 40 years and twice in that time I have had older battery's suddenly short internally and leave us sitting (cant jump start them). The last time was just a few years ago on a used car I bought.

You have a Leece-Neville part # 79000 voltage regulator. Verify your voltmeter is not lying to you. Go online eBay and query 79000 voltage regulator. Transpo brand HD model is good. These are flat compensating regs so LN decided. No temp adj slump. LN brushes for the 2500 series JB units are long. I never liked OEM 79000 regs so I used Transpo with good luck. DO NOT use a reman alt as they are JUNK except for the Prestolite Leece-Neville remans available at big rig manufacturer's parts counters. Stick with Transpo for regs and OEM for new or reman units.

MEXICOWANDERER wrote:
You have a Leece-Neville part # 79000 voltage regulator. Verify your voltmeter is not lying to you. Go online eBay and query 79000 voltage regulator. Transpo brand HD model is good. These are flat compensating regs so LN decided. No temp adj slump. LN brushes for the 2500 series JB units are long. I never liked OEM 79000 regs so I used Transpo with good luck. DO NOT use a reman alt as they are JUNK except for the Prestolite Leece-Neville remans available at big rig manufacturer's parts counters. Stick with Transpo for regs and OEM for new or reman units.

Thanks. I wrote that if the new chassis batteries end up having no bearing on my problem, that I would simply replace the voltage regulator. I reasoned that it was obvious that the charging part of the alternator was working, therefore it has to be something telling the regulator that a high charge rate is called for, OR the regulator has failed somehow. Yes, the brushes are long, I replaced them a few years ago (one of them was broken in half). But, the symptoms then were quite different than what it's doing now. Thanks again, and I'll report later (I'm off to Sam's to purchase a couple of group 31 RV/Marine batteries).
Oops, I'll verify the high charging rate at the alternator (not an easy check). I'll check it at the batteries first.