If you ever worked on old mopar wiring, especially the charging system, you are in for a treat. When I rewired the Power Wagon project truck I wanted to upgrade the wiring to handle modern day loads. This involved installing a new blade style 12 circuit fuse box, electronic ignition, new alternator and electronic regulator just for starters. The wiring upgrade was not too difficult and upon initial start-up of the rebuilt poly 318 everything seemed okay except for the charging system. It seemed like no matter what I tried the battery was not getting a charge from the alternator.
After some indepth research on the topic I learned that Mopars old school wiring for the charging system was just that, old school. It was probably one of the worst wiring configurations for long term dependability ever, so you can imagine how it functioned on a 43 year-old truck.
Basically Chrysler took 12 VDC from the battery and routed it through the bulkhead (#1 connection) went up to an ammeter on the dash (#2 connection), out the other side of the ammeter (#3 connection), to three branch wires off the main wire (#4 to headlight switch, #5 to fuse box, #6 to ignition switch) and then the main wire goes back through the bulkhead (#7 connection) and the circuit completes itself at the alternator battery post (#8 connection)
So, you can only imagine what could possibly go wrong on a 43 year-old truck’s wiring system when the wire carrying all of the current to the system and back to the battery goes through 8 separate connections. In addition to this problem when you install electronic ignition and an electronic regulator the metal casings need to have good grounds to the newly painted vehicle body for everything to work. My first step was to make absolutely sure there was a good ground at these 2 boxes and since it was a fresh rebuilt engine installation I also double checked for a good ground from the engine to the vehicle frame, and from the engine to the truck’s cab. I will tell you that before you waste any time troubleshooting any wiring problem on an old Mopar make sure all these grounds are good. If not you will never find the problem you are looking for.