Alternator Shuts off?

[harborc]

Hey everyone, my first post and a little confused by my 2015 Silverado charging system. I know it has the EPM system but after driving for a few hours I noticed the voltmeter was just inside the left normal line about 12 or so volts. No messages or chimes but didn't seem to be charging. After stopping for gas and restarting the volt meter shot up to a little above 14 volts for about 1 - 2 minutes and slowly returned to the left most normal line. After returning home the volt meter still showed what seems to be low voltage so I checked with a multi meter and got 12.8 volts. shut the engine and checked again and still 12.8 so NO charge at all while running. After restart volts always go up to 14.2, so is this normal operation for this vehicle? I have other fairly new vehicles and none do this. Thanks and I'm sorry if this has been posted before but don't want to make a trip to the dealer if this is normal!

[DaveH71]

Normal operation.

[harborc]

Thanks Dave.

[sams819]

NORMAL

[OutBurst]

It is designed to do that in order to prevent overcharging - usually happens after extended (over 20min) driving at sustained speeds. I had the same complaint.

[fondupot]

There is a nice blurb about this in your owners manual. I suggest you crack it open and read up on it.

[sahls01gmc]

This threw me for a loop the first time I saw it. Makes sense though, I can see the alternators lasting longer now if they're not constantly charging.

[harborc]

Thanks for the replies, I do feel better knowing that this is normal operation. I did read the owners manual, cover to cover but the chapter on charging system only states the charge will drop somewhat but it says nothing about the alternator completely shutting off. I had the same exact voltage at the battery with a multi meter while the engine was running as I did with the engine shut off. Not charging. It stayed at that voltage almost an hour while driving. a little concerning. thanks for the quick replies.

[Georgia1911]

This threw me for a loop the first time I saw it. Makes sense though, I can see the alternators lasting longer now if they're not constantly charging.

 

Even more so batteries, as they will not be overcharged.

[pl8man]

I went through the same thing, normal, I don't like it, but normal!

[ZXTOM]

Normal operation of charging system

[sailormandave]

Apparently this normal but there is nothing in the owners manual about it. It happened to me this weekend and I was 300 miles from home.  AND of course after business hours at the nearest dealership.  Ruined my entire weekend worrying about if I was going to get back home.     Its scary and I wish the dealer would have told me about this.  

Edited October 30, 2018 by sailormandave
add photos

[Nasty]

It has been like this sonce 2005 models. There is a battery current sensor on the ground cable that monitors this. 

[sailormandave]

First GM product since 1996 pu.  SURPRISE!!!!

[bagger97]

You can override this by turning on the headlights. It will stay at maximum output.