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over charging battery question


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Hello all,

I know my batteries in my dodge 5.9 are getting week.   If it sets for a few days or we have a night below 45 degrees usually requires me to get the jumper cables.   Anyhow, on my way to work this morning, i noticed my lights seem to flicker a bit.   Gages usually charge around 13.5-14 volts would jump to 15-16 volts.  If i let off throttle, it would go back down to 14.   All the way to work, this would happen.   Is this bad batteries or do i have other issues?   Planning to stop for new batteries on my way home.   No i have not used the multimeter yet.  Thanks for any imput.

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I had a regulator go bad in an Autozone rebuild.

It would peg the voltmeter and then down to normal.

This was happening every second and it made the dome light look like a flash bulb.

They replaced it.

Cheap Chinesium voltage regulators.

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You did not say what year Dodge, but you said batteries not battery, and 5.9, so I assume you mean Cummins, not the gas 360 V8 engine. Batteries as they age out let lead sludge build up in the bottom of them and can start to internally short out causing the alternator to try to charge stangely, or it will start okay, then you park for just a little bit and you go back out to restart it to leave and little or no crank, I have had that happen. Depending on the year of the Dodge Cummins, on the 94-02 models, the ECM controls the charging on those.  You could test and or replace the batteries as a good start, alternator would be next, this assumes your connections are clean. Another thing to look for is if it goes to charge really high and after a bit quits charging, one or both of your two relays for the intake heater grid have stuck on, I have had that happen a couple times. You can disconnect the wire on the driver's side battery to get the intake heater grid to shut off if that was to happen.

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Check all voltages and grounds. There are several grounds to check. Obviously the engine but also the body and computer or regulator. Check for bad connections and wires. You know, open the hood and give her a general checkup!

The voltage regulator was separate on the early first gen trucks. 91.5 through 93 had the regulator in the computer like the second gen. 

If  the regulator in the computer goes bad it can be bypassed and replaced by an earlier style regulator (at least on the first gen Cummins).

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