1999 3500 Cummins diesel electrical problems

mrmick

I have a 1999 4x4 dually Cummings diesel with 2 optima red top batteries which are about 3 years old. Everything will work o.k. for a month or so and then what seems to be out of the blue, the batteries are to dead to start the truck. I think that it has happened more when the weather is cold. Last night, after sitting for a few hours, it struggled to start and then while driving home the headlights flickered every few seconds. And then this morning, after a 35 degree night, there was not enough juice(?) to start it.And then it took a little while to jump start it. I can build you a house but not your engine. Any ideas? Thank you ahead of time.

grizwald1

I have a 1998 and found the wire coming from the alternator to the power box on the opposite vendor was rubbing on the top of the shock. It was shorting out intermittently. This is before the 120AMP fuse link and the battery so it was basically dropping the voltage and under charging the batteries. It really dropped the batteries when I ran the lights.

grizwald1

Have a 1998 3500 which has the batteries, alternator,and starter replaced. Found the cable from the alternator was intermittently shorting on the top of the shock mount where it ran up to the electrical box. I fixed that. Now once the truck is started, it progressively drops the battery voltage to killing the truck. Have taken out all the fuses, relays, and fuse links only leaving the ones needed to make the truck run. With two fully charged batteries, it runs the battery voltage down to 11.65 with the truck running. After leaving it running the voltage keeps dropping until eventually killing the truck, at about 8.25 volts. Any help will save the rest of my hair from being pulled out.