I had a charging problem to begin with on my 2001 ram 2500 van with 255K mi on it. I pulled the alternator and had it tested and it was good. So I put it back in and it was charging again and then stopped. It killed the battery. So I got a new battery and pulled the alternator wires to do a short test. (volt meter from the negative battery post to the negative wire) it showed 12.6 volts even with the alternator disconnected. I put it all back together and it's charging now. I know I may have to get another alternator soon. But when I disconnect the negative battery terminal and run the volt meter from the post to the wire it still shows 12.6 volts. I have mad sure the dome light was out and pulled each individual fuse and relay one at a time and testing for the voltage. Both at the fuse box on the drivers side of the dash and in the engine compartment by the battery. It always shows 12.6 volts. Anyone have a likely place to look for the short?

 

Why does having 12.6 volts like that make you think there's a short?

 

The Haynes manual says that having voltage between the negative battery post and the negative terminal indicates a power drain indicating a short. But after reading a bit more I found it may be standby voltage for the pcm. Maybe it's normal. any idea?

 

That, or if there's an installed alarm system, remote start, keyless entry, clock, or an electronic controls radio.

 

it's a plain jane work van. no frills only the stock radio. but the voltage is there even if I pull the fuse for the radio and the pcm.

 

The PCM, TCM (Transmission Control Module), BCM (Body Control Module-if your van has one) and Clock Radio will have residual power even with the key off. If you pull the clock memory fuse for the radio and PCM then pull the Trans fuse then all should be shut down.