Voltage meter dipped to 11 and stays ... no battery light.

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On the way back up to the US currently Nicaragua. I noticed that my voltage guage was reading lower than it should ... maybe 11 or so. No battery voltage light ... group 31 battery 5 years old. Headlights aren't dim or anything and she starts up fine ... I stopped, checked terminals etc. I don't have a voltage meter with me. Voltage indicates the same even under acceleration and a high rev blip on the throttle makes it move up a fraction but barely noticeable. I'm thinking windows are on a battery lead circuit and headlights off the alternator? Hunch is a bad cell in the battery. It's middle of the night here and not really any place to check it out at the moment. Had to hunt for a bit to find cell service. Thoughts ?? Maybe check the magnetic pull on the alternator... if that will tell me anything on these 100 series. Should I do the old school pull the negative battery lead off while she's running and see if she still runs? Shut her down before reconnecting and all? Or will this toast my electronics like in new BMWs? Checked the fuses and all look good to go. Strange the battery light isn't on, but maybe because that measures output from the alternator as d the batter is showing low voltage on the dash because a cell is toast?

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I’d suspect alternator.

You say that you don’t have a multimeter, which would probably be my first tool of choice, to see if it’s a gauge issue, or an alternator issue.

Do you have any OBD2 tools (ScanGauge/Dongle that connects to your phone/TechStream/iCarsoft) with you that might read voltage?

Is the under hood “ALT-S” fuse intact?

Any chance that a local parts store would have one of the cheap battery/alternator testers like this:

 
if it's a bad cell, wouldn't the alternator still put out the 14+V which would show on the dash? And I think you'd see changes when rpms fluctuate, after starting etc.
First guess would be alternator then. However, it's surprising it starts fine and the headlights are good at 11V. So could be the dash voltmeter too, I suppose. However, this being Nicaragua, I'd prepare for an intervention in an urban area cuz if it's the alternator you're driving on borrowed time. And I would not do any shenanigan with connections that have the remotest chance of damaging electronics. Better to plan for a couple of cheap nights in a hotel, good food and cerveza. Take your time if you can! Best luck to you!
 
There is a relay soldered onto the circuit board under the fuses in the fuse box on later 100s.

I had an issue with my relay, it wasn't getting triggered and the alternator wasn't putting out enough voltage (in any).

One thing that I did notice was that when I had the issue, the battery light wouldn't come on when I put the key in the on position but didn't start the car.

I ended up taking the circuit board out and sanding the contacts on the relay. Havent had the isue since.

I have a thread on it from july/august 2020. I think I wrote more about it at the time, but don't remember and can't quickly find it as I'm on my phone
 
It does sound like alternator, and you may see Battery light while running soon.

Some cheap insurance and to aid in diagnostics, while you sorting out. May be to toss in a fresh 27F. Which is likely easier to get your hands on than an alternator where your at. Obviously if it then shows ~14V on gauge and continues to do so, your golden. A second bit of insurance, you may find in third world country. Is a solar battery tender. Then you can keep the second battery, on board charged. Last thing you want is a no start condition in a remote location.
 

with the key in the "on" position, check to see if you have voltage on either side of the IG-FR fuse. Your picture above of the truck no running but ignition on, looks very similar to what my issue was.

if you don't have voltage on either side of the IG-FR fuse, it could be the relay I noted in the post above. I was able to diagnose it for myself as a result of the issue being intermittent. I went through 2 alternators in the process of determining that the alternator wasn't actually the problem.
 
My vote is a bad cell in the battery. Alternator is putting out fine most likely but with a bad cell you are not going to see 14 volts on the gauge.

The symptoms point to that instead of the alternator. Otherwise the voltage would quickly drop to 10 or below and it would no longer start or run.

You shouldn’t have any trouble find a group 24 or 27 replacement battery even in rural Nicaraguan/Guatemala/Mexico.

Get a new battery for piece of mind and enjoy the trip!
 
Also pointing to a bad cell are the rough road conditions which have broken one of the lead connections inside the battery. I don’t recall any smooth roads last time I was there
 
well, IMO, it was a bit cheeky to go on a trip like that with a 5 y.o. battery. So, since it's on its last legs probably in any case, if it can be had at reasonable cost I'd get a new one. Put the old one in the back as a backup, and see what happens with the fresh one. But yes, I would think that even in Nicaragua you can get a cheap chinese multimeter for not too much money.

Do you see the battery symbol light on when you turn the key on before starting the engine? (Don't recall for sure that it shows on the 100, but I would think so.)
 
Yes battery symbol illuminates before starting. It is "trying to charge" it seems intermittently ... I got another bump just right and voltage went up. I can not find any loose wires. Ground is good etc. At a shop now and they actually have a battery tester and telling me they think the battery is bad. However they only have a group 34 battery. Hahaha ... anyone try a GROUP 34 OPTIMA before? Wondering if it will work ...
 
Yes battery symbol illuminates before starting. It is "trying to charge" it seems intermittently ... I got another bump just right and voltage went up. I can not find any loose wires. Ground is good etc. At a shop now and they actually have a battery tester and telling me they think the battery is bad. However they only have a group 34 battery. Hahaha ... anyone try a GROUP 34 OPTIMA before? Wondering if it will work ...

A group 34 would need a ~1” spacer under it, and it will fit about like a 24F (with the spacer). I don’t remember if you want the “R” or “non-R” to have the posts on the correct side.
 
Yes battery symbol illuminates before starting. It is "trying to charge" it seems intermittently ... I got another bump just right and voltage went up. I can not find any loose wires. Ground is good etc. ... ...
Check ground to engine as well as to battery. Check for corrosion under body/frame bolts. And then the plug to the alternator - sometimes needs a bit of cleaning, and check the spring force of each pin.
 
I found another battery ... group 27. Got that one. Tested again and says the voltage regulator is not working properly. Seems that's what drained the battery and why sometimes I would get 14 volts of charging and sometimes it would read 11 volts while I was driving it seems. Wondering if there's a way to locate the voltage regulator on the alternator and clean it?
 
I'm sure you are a much more seasoned traveller than I am, judging from your current adventure. Good thing given that a (perhaps Gringo-looking) fella travelling with an ultra-luxury vehicle by local standards that is experiencing trouble in Central or S. America must look like an amazing ka-ching opportunity for the (hopefully rare) less scrupulous shops down there. I'd keep an eye out to avoid the unexpected problem developing with oddly-needed parts, fried electronics etc. Best not to get stranded. Actually, for that matter, I'd keep an eye out for that in some shops in the US too... Good thing is that most mechanics down there seem very resourceful and helpful and good people.
But that all only makes the adventure more interesting. Good times, good memories! Enjoy!
 

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