i have a 1980 d150 and a previous owner redid all the electrical and its a mess but right now im havin a problem with the alternator not charging the battery even though both are still good if anybody could help me with this problem i would greatly appreciate it.

 

need to know a bit of info. need to know what is the voltage at the battery and the large lug on the alternator is with and without the truck running. also knowing what the voltage is at the 2 smaller wires on the alternator might help. could just be a bad voltage regulator.

 

The external voltage regulators are grounded by the mounting screws to the firewall. A bad ground is a common problem in our trucks.