I have an 02 ext cab cummins. i was driving to get dirtbike parts got home worked on it (the bike) went to leave down the road my alternator stopped charging. but when i drive down the road decent rpms an engine load the alt will charge but when im off the throttle the tranny down shifts due to lack of voltage... figured alt was bad. ordered brand new one from chrysler still didnt charge.. checked fuses an relays nothing bad.. sent it to chrysler stupid me spent over 500 to get an answer that my cam sensor.. now all excited took it home did it myself still nothing. tac worked before i changed the sensor anyways an my truck doesnt have a crank sensor.. so we took the green an blue wires off the alt an checked for continuety (however spelt) there was no signs of a break or short in the wire... but... i did borrow my uncles 01 cummins pcm an tried that an still nothing. im wondering if the pcm from another truck isnt programmed to my truck or anything. all of my grounds are sanded and cleaned.. HELP????

 

Alternators have to be on a revolving circut or they dont work it sounds to me like something is bad inline ...batterys,ground maybe your voltage gauge/sensor get the old shock box/ohm meter and start tracing