Ok I know I have seen one do this before but can not remember what caused it and was wondering if anyone else has had this. 1999 Dodge 2500 altenator does not charge on the vehicle but test good on the bench.... I think it is in the pcm but can not remember ... thanks for your help Wayne

 

the pcm is what tells it to charge, i had one that didn't charge on the truck, and on the local auto parts store tester it passed everytime. i gambled and bought a new one and it fixed it. charges fine now. but im not saying this is your situation.

 

mine did the same thing, bought a new one yesterday from napa and i haven had a problem yet, it charges fine

 

something you might also want to check the dodge alts are really bad about the signal wire plug getting loose of not making a good connection if you move the plug around and it starts to charge the clean it and check the contacts in it.

 

#1 cause in our shop is a bad PCM ground. There should be a ground cable from the side of the PCM to the body, clean both ends of the cable and a bit of paint off the body and 90% of the time you'll be fixed up ready to roll!
PS this is a very good cause of a no fault test on a tester. Load testing will sometimes cause pcm to properly regulate voltage. Just a thought.

 

1st check your your FUSEABLE LINK located in the fuse box under the hood, i thought my alt was bad turned out it the link was burned out. put a new one in and walla! now i keep a spare in my truck.. check that first!!!!

 

Wowza! Isn't that fuse 140 AMP? You alternator must have spiked or something!

 

No doubt, if that's bad there is most likely other issues unless it was damaged by vibrations or something of that nature. That's not a very common failure.