Battery overcharging Check gauges

[Revery]

2007 Dodge 2500 with Cummins 5.9. Check gauges light came on and I discovered the battery connected to the alternator overcharged so much it blew the cap off. Batteries only 2 months old. Took battery back and replaced it. Let truck run for about 10 or 15 minutes and it started again overcharging the battery, check gauges light came on again and it started running rough. Seems like alternator issue, but I was told that the alternator may be controlled by the ECM. Does anybody know the issue, or experience it or know what to do the correct? Thanks all.

 

[Revery]

Also forgot to mention when I cut off all circuit power by pulling the fuse (number 10 if I remember) it will still drain the battery.

 

[Fast69Mopar]

2007 Dodge 2500 with Cummins 5.9. Check gauges light came on and I discovered the battery connected to the alternator overcharged so much it blew the cap off. Batteries only 2 months old. Took battery back and replaced it. Let truck run for about 10 or 15 minutes and it started again overcharging the battery, check gauges light came on again and it started running rough. Seems like alternator issue, but I was told that the alternator may be controlled by the ECM. Does anybody know the issue, or experience it or know what to do the correct? Thanks all.

This issue is an indication of a corroded/failed crossover cable between the batteries. The ECM reads battery voltage from the left/driver side battery and the alternator directly charges the right/passenger side battery.

If you check the voltage on the left/driver side battery with the engine running you will more than likely find a lower voltage than the right/passenger side battery.

 

[Revery]

Thanks folks, this sounds reasonable. Would it also cause the batteries to drain even when the shut-down fuss is pulled? My task for Saturday morning.

 

[Fast69Mopar]

Thanks folks, this sounds reasonable. Would it also cause the batteries to drain even when the shut-down fuss is pulled? My task for Saturday morning.

No, this overcharging issue will not cause a parasitic draw in the batteries. You will need to go through the electronics in the truck to determine the source of the draw.

I like to use a combination of my
DVOM (volt meter) and a light bulb. I use a turn signal bulb in a 3157 socket and connect it to the battery along with my DVOM to monitor voltage. I use the light as a visual aid.

When looking for a parasitic draw in a battery I start by disconnecting the easy to access electrical items in the truck and I watch the light bulb to see if it goes out or if the intensity changes. If I don't get the desired results with the easy stuff I then start disconnecting the big items like modules.

Don't disconnect more than one item at a time and if you disconnect something and you don't see a change in voltage or light intensity plug it back in and move to the next item.