Why does my 97 Dodge 2500 (cummins)loose.

ANONYMOUS

MEMBER
1997 DODGE TRUCK
500,000 MILES

Why does my 97 dodge 2500 (cummins)loose battery power while im driving?
we bought this truck and were having fun with it, runs like a beauty. Saw a friend on the side of the road and went to say hello.
shut off the truck and found the batteries had lost enough power to keep the truck from starting. So we got an alternator tester and found that no power was getting to the batteries. We put a new alternator in it and it worked great for a few hours. Shut off the truck happy, but only to find it starting slow, and it started slow a couple of times befor it wouldent start at all. Cant figure out how to go about this. CAN YOU HELP ME?

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

Could have bad batteries. Measure the voltage with the engine off, then again with it running. With it off you should find 12.6 volts if they're fully charged. At 12.2 volts they are good but discharged. If you find it closer to 11 volts, disconnect one of them and measure each one individually. 11 volts indicates a shorted cell and that battery must be replaced.

With the engine running, the voltage must be between 13.75 and 14.75 volts. If it is low, measure the voltages on the back of the alternator with the engine running. If the voltage on the fat output wire is different than across the batteries, look for a blown large bolted-in fuse in the under-hood fuse box. If the voltage is low there too, measure on the two smaller wires on the back of the alternator. One must have full battery voltage. The other one must have less but not 0 volts. If it has 0 volts, the brushes are open, (worn), and either they or the alternator must be replaced. If you find exactly the same voltage on both wires, there is a break in the circuit after that point, either in the wire, a corroded connector terminal, or the voltage regulator itself inside the Engine Computer.