Maybe someone has been through this before so here goes. I am working on a 1997 3500 with a cummins/5speed. My uncle asked me to change the alternator so I did without asking questions. After changing the alternator, the tach and voltmeter were working sporadically. Then I asked him about what it was doing before, and he said that was the whole problem. I pulled the alternator off and it of course being new, checked out fine. There is only 0.9 volts at the two small terminals on the back of the alternator with key on and now it won't charge and tach doesn't work. Battery voltage is around. 12.8 volts. No moving of wires/loom changes anything and the VSD Relay has voltage where it's supposed to. Is this the pcm? There are no trouble codes. PLEASE help, I am out of ideas. Thanks.

 

And is there any way to bypass the voltage regulator in the pcm to recheck the alternator on the truck?

 

comeon guys. someone here has to be able to help me out. where are all the dealership guys at?

 

well, thanks anyway, but I figured it out today. The crankshaft position sensor was bad. It evidently works in conjunction with the pcm somehow to start the generator driver.