Battery voltage fluctuating.

[ericv]

Same issue but I also had the battery light and the "Service Charging System" warning come on the dash. Battery and Alternator tested fine, but the battery was a bit old and it's the wife's car so I put a new one in it anyway. Five days later I just got the same light/warning. Cranks fine to start, runs fine, but the volt gauge is doing exactly what was pictured at the top of this thread. Is this the same AGM stuff, or with that warning light do I have something else going on?

 

[olliec420]

So on my 09 Yukon I just had my 3rd random shut down while driving this year. Two times while I was slowing down to a red light. Pop in neutral and turn key and fires right back up like nothing is wrong. I read a while back that could be due to the battery cables going bad and that's a known problem on this gen. Can any one confirm that? Could that be what's happening with the voltage fluctuations this guy is having? Mine fluctuate too (new OEM alternator last summer). Battery is 3 years old this year and seems to be great. Im hoping battery cables.

 

[the 18th letter]

Also worth nothing: If you're running a Range AFM module it'll never enter the fuel saver mode, charging voltage always stays at about 14.5V.

Thread dig, but is this confirmed. Running a Range AFM and I’ve noticed my voltage fluctuates since I replaced the battery a few weeks ago.

 

[15burban]

Thread dig, but is this confirmed. Running a Range AFM and I’ve noticed my voltage fluctuates since I replaced the battery a few weeks ago.

Have a range on our 15 and it fluctuates. I don't see why the range device would stop the fluctuation.