Voltmeter Reading Low?

Dunc · January 22, 2015

I noticed yesterday that the voltmeter in the dash is reading ~12.5v. It happened again today during lunch. It may have happened before yesterday, but yesterday was the first time I noticed it.

I haven't hooked up my multimeter yet to verify this reading, but I'm assuming it's reseasonably accurate. The truck only has 680 miles on it currently. Does anyone else have this issue? If that reading is correct it's leading me to believe I have a problem with the alternator because that reading should be more like ~14v while the engine is running. It doesn't always read this low while running. Sometimes it is ~14v which is normal. Thoughts?

MMC · January 22, 2015

Perfectly normal.

00Silverado4x4 · January 22, 2015

Not an issue at all. GM has been using a on-demand charging system for quite a few years now.

Dunc · January 22, 2015

Well that's a relief, I was looking at it thinking "please don't die on me battery" as I was going down the highway. Thanks for confirming.

Shimmy Bang Bang · January 22, 2015

So in other words, the reading displays ~12.5 when after starting it and then goes back up to ~14 eventually (soon after)?

dcarl · January 22, 2015

I noticed mine from time to time will drop to 12.5. Even measured it with a digital multi-meter and called the dealer to make an appointment to take my truck in, then read a number of posts about these trucks and the on-demand charging systems. You'll notice that with the lights on, it will usually run up around 14 volts. Mine only appears to drop down to 12.5v during the day when nothing else is on and requiring extra charging, so after I read up on the charging system, even though I couldn't find anything in my manual that really breaks it down like previous models, I called my dealer and cancelled my appointment.

Haven't been stranded yet. Definitely takes some getting used to. I went from an 01' Denali XL that always stayed up around 14v when the charging system was working properly and the minute it wasn't I knew it, so when this one dropped to 12.5v it alarmed me too.

Dunc · January 22, 2015

^^^Now that you mention it, both times have I've noticed it were also during the day when the headlights were not on. It definitely is alarming. Makes it pretty much impossible to spot a voltage problem and react before it leaves you stranded with a dead battery going down the road.

So in other words, the reading displays ~12.5 when after starting it and then goes back up to ~14 eventually (soon after)?

Sometimes it's at 14v the entire time I'm driving (to my knowledge since I'm not glued to watching it.) Other times it's at 12.5ish the entire time I'm driving. These past two times when it was at 12.5 it was for a 40 minute trip and then today was a 20 minute trip. I was not aware of the charging on demand thing so unless my battery dies while driving then I'll just ignore the voltmeter.

fondupot · January 22, 2015

it will fluctuate between the two hash marks on the voltmeter, depending on current load.

txchevy4ever · January 22, 2015

Even my 2006 Tahoe did this. It's perfectly normal, and another reason you want to run an isolator if you run 2 batteries.

xkvator · January 23, 2015

no load = better gas mileage. although miniscule, every bit helps with their CAFE ratings...

on my '11 Silverado, I noticed it wasn't fluctuating, as it should...took it into a dealer here in ohio to have the deteriorated tailgate bowtie replaced, and had them check the charging system...said everything was ok, and whatever they did while checking, triggered the voltmeter to fluctuate as normal...

mafd2 · February 20, 2015

I noticed mine from time to time will drop to 12.5. Even measured it with a digital multi-meter and called the dealer to make an appointment to take my truck in, then read a number of posts about these trucks and the on-demand charging systems. You'll notice that with the lights on, it will usually run up around 14 volts. Mine only appears to drop down to 12.5v during the day when nothing else is on and requiring extra charging, so after I read up on the charging system, even though I couldn't find anything in my manual that really breaks it down like previous models, I called my dealer and cancelled my appointment.

Haven't been stranded yet. Definitely takes some getting used to. I went from an 01' Denali XL that always stayed up around 14v when the charging system was working properly and the minute it wasn't I knew it, so when this one dropped to 12.5v it alarmed me too.

My '14 Sierra does the same thing. Was thinking about letting dealer check it but I guess it's normal. Goes from 14V then down to 12.5 then back up. Didn't notice my '13 doing that but maybe didn't notice.

txchevy4ever · February 20, 2015

Battery Load Management The vehicle has Electric Power Management (EPM), which estimates the battery's temperature and state of charge. It then adjusts the voltage for best performance and extended life of the battery. When the battery's state of charge is low, the voltage is raised slightly to quickly bring the charge back up. When the state of charge is high, the voltage is lowered slightly to prevent overcharging. The voltmeter gauge or the voltage display on the Driver Information Center (DIC), if equipped, may show the voltage moving up or down. This is normal. If there is a problem, an alert will be displayed.