Alternator indicator help

[siego99344]

Good afternoon my fellow people. I ran into an issue I have a 2015 gmc Sierra 1500 V8.  My issue was with alternator battery indicator gage on dash. Normal the indicator would be at 14. Recently it’s been at 11-12. Took it to Autozone battery and alternator were good. Went to orailies or however you spell it and says both are bad. Every now and then gage will be at 12 and other times it will be at 14 like normal. What do I change. I checked for loose wires and corrosion and everything is tight and looks clean. Any help would be greatly appreciated thank you 

 

 I did forget to mention when I first turn on truck it starts out at 14 then after a minute or 2 it would gradually start to decline and stay at 12 volts. But sometimes I start the truck it would start at 14 and stay at 14 

Edited January 7, 2023 by siego99344

[BO TIE 1]

Any starting issues or trouble codes?

[siego99344]

No trouble codes. If I leave the truck off for more then 1 day it dies and I have to jump start it. 

[rav3]

To me, I would check your grounds. Remove the battery ground & clean it with a battery brush, both the cable & battery post. 2nd, I'd remove the grounds that are located on the body, clean & reconnect, using some dielectric grease to limit corrosion. here's a good video.

 

[BO TIE 1]

If that's the original battery probably on it's way out. 

[siego99344]

1 minute ago, BO TIE 1 said:

If that's the original battery probably on it's way out. 

It was the same battery that has been on the truck when I bought it 2 years ago. Before that I wouldn’t no. But would a bad battery show my gage only charging at 12.6 colts and not the original 13.8-14.6 I can change the battery no issue but my concern would be buying new battery and it going bad 

[CamGTP]

Are you using a multimeter to watch the voltage or just the dash itself?

 

The alternator is computer controlled and if you have no warnings on the dash for the charging system, the alternator is working as required by the computer. They will charge at voltages of roughly 12.9-15 volts depending on need.

 

If it was me I would drive the truck to charge the battery fully, unhook the battery to isolate it and use a multimeter after a day to check the voltage on the battery. If it goes from 12.5-12.7 volts down into the 11's or lower just sitting by itself, the battery is no good.

 

If the battery doesn't drop voltage then I'd be looking for a draw on the battery and dirty grounds.

[siego99344]

18 minutes ago, CamGTP said:

Are you using a multimeter to watch the voltage or just the dash itself?

 

The alternator is computer controlled and if you have no warnings on the dash for the charging system, the alternator is working as required by the computer. They will charge at voltages of roughly 12.9-15 volts depending on need.

 

If it was me I would drive the truck to charge the battery fully, unhook the battery to isolate it and use a multimeter after a day to check the voltage on the battery. If it goes from 12.5-12.7 volts down into the 11's or lower just sitting by itself, the battery is no good.

 

If the battery doesn't drop voltage then I'd be looking for a draw on the battery and dirty 

18 minutes ago, CamGTP said:

Are you using a multimeter to watch the voltage or just the dash itself?

 

The alternator is computer controlled and if you have no warnings on the dash for the charging system, the alternator is working as required by the computer. They will charge at voltages of roughly 12.9-15 volts depending on need.

 

If it was me I would drive the truck to charge the battery fully, unhook the battery to isolate it and use a multimeter after a day to check the voltage on the battery. If it goes from 12.5-12.7 volts down into the 11's or lower just sitting by itself, the battery is no good.

 

If the battery doesn't drop voltage then I'd be looking for a draw on the battery and dirty grounds.

I took the truck out this morning I drove it maybe hr or 2. The only reason I see the voltage was taking it to Autozone and orioles they hooked up their machines to it. When orailies hooked it up the voltage thst the alternator was putting out went from 14 to 12.1 in there somewhere then it stayed there. But if I don’t turn the truck on for at least 2 or even 3 days it won’t start I have to charge it to turn it on. 

[siego99344]

A little update. Truck has been sitting there for at least 2 hours went outside to see if it turned on it did. So I took it for a drive and everything is normal. I don’t understand. I checked the grounds they were good I remember having an issue with the grounds during summer. But checked them again and clean. This was a picture while I was driving around right now. I turned on everything to put a draw on the alternator and it didn’t move 

[rlcole321]

I have a similar condition sometimes. I have 2 vehicles, a one car garage, and a neighbors sprinkler system right next to my driveway, so to keep the Nasty ground water off my truck (which the high calcium and sulfur content really misses up the paint if it sits to long on it!!) I have to start it and move it a lot, so the battery doesn't get charged enough sometimes if I don't drive it for a while or a lot of short distance runs, I have to put the charger on it every once in a while, to keep it up. But, like Cam said, it has adaptive charging, so it reduces the load on the alternator when it's not needed.