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ram 2500 diesel alternator or voltage reg in ECM

03-03-2012, 07:46 AM
got a check gage warning and noticed my charging circuit gage had flat lined; gage will go back to about 12 volts after a restart but drop again after driving a mile or so. had the alternator checked while still on the truck and it is showing the same as the gage. Im going to take it off and have it bench tested but evidently the voltage reg is in the ECM now. original alternator with 280,000 miles on it. If alternator tests OK any ideas on where to look next? I drove for about an hour after gage flatlined; lights didnt dim, truck starts right up with no problem. batteries read 12.5 volts> thanks for any feedback.

Chris Stewart
03-03-2012, 11:33 AM
What year Dodge?
What does the voltmeter on the instrument panel show when the voltage is low?
I put brushes in mine after I started getting low voltage MAP & IAT codes.
They're ok now.

03-03-2012, 04:28 PM
sorry...2002. the dash voltmeter reads about 10-12 when it does read but drops to 8, the lowest it can read, when the dash warning comes on. I think it would drop to zero if that was available. its like the gage gets turned off. strange thing is there doesn't seem to be any loss of battery power to start etc after I kept going about an hour after the first time the gage dropped. Thanks

Chris Stewart
03-03-2012, 06:24 PM
You might try cleaning all the battery connections.
If you take them all loose, the computers and modules will be sorta rebooted when you hook up the clean connections.
There are some nuts and screws for tightening connections inside the fuse box under the hood, you might check them too.

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