Cummins over voltage charging

shelby27604

shelby27604

Well-Known Member
Joined
Jun 6, 2013
Location
Efland NC
My 2006 Cummins seems to be over charging the batteries. When I check voltage while running, each battery reads in the 16.6V range. Engine off, battery voltage measures 14.4~14.8V.

The truck is still new to me, so I don't know a lot of history, but both batteries are less than a year old, I have cleaned the connections and terminals of both batteries.

Is the alternator regulated by the ECU ? Do I pull the alternator and get it tested, should I be replacing cables, am I looking at a faulty regulator ?

On my YJ I had to buy a kit to install an external regulator, is that the best route here? Suggestions and direction appreciated.
 
Is yours internal or externally regulated? If internal look to the alt if external then it’s usually controlled by the BCM. This is a common problem with the second generation dodge that has the regulator just outside of the alternator in-line with the wiring and they are known to go bad so people actually use an old-school 70s MOPAR external regulator and bypass to trigger the alternator to charge. That is how mine is and it works just fine but I don’t know about your vintage
 
I do know the system looks at the voltage of just one battery, and will over charge both via a faulty wire on the voltage sensor circuit. Mine tried to explode going down the highway.

Cleaned up and replaced the high resistance wire causing the faulty value and it settled down. The regulator I believe is part of the horrible electrical management plan they came up with called a TIPM. If this is the source it can get ugly expensive.

edit: Gears Magazine - A Common Sense Approach to Charging System Diagnosis bottom of article gets to describing a check for CHRYSLER type systems.
 
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It reads one battery and charges the other. I worked on one 06 that literally melted the terminal off. Most of the time it is the positive cable that connects the two batteries. The ends will look fine and the cable in between corroded and swollen.
 
Hurdt299 said:
It reads one battery and charges the other. I worked on one 06 that literally melted the terminal off. Most of the time it is the positive cable that connects the two batteries. The ends will look fine and the cable in between corroded and swollen.
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I can see corrosion on the cables, I am just going to throw new cables at it. It seems like a common enough problem, I would rather they all be new and not an issue on a road trip (underwood fires have a way of derailing a trip).
 
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