Ok guys and gals. After doing some researching and studying old pics I had, I have come up with a diagram that will show you how to wire in an external voltage regulator for when your internal regulator in the PCM quits working. Symptoms are either no charge or overcharge, however they are designed to fail in a no charge state.
After insuring your alternator, batteries, and crank sensor are all good you can then use this diagram and save yourself about $800 on a new PCM. The alternator is a open field external regulated type. There fore it makes it easy to do this mod.
What you will need is a voltage regulator from an 89' or older Dodge/Chrysler vehicle, a plug with harness, several pieces of wire, three barrel crimp connectors, two small ring and one large ring connectors, crimp tool, black tape, cordless drill, 2 self tapping sheet metal screws.
First you will need to find a secure place on the fender well or firewall to mount the voltage regulator. Once a location is selected make sure to Sand the area down to bare metal where the screws you use to mount the regulator will make a good ground. Then on the back of the alternator you need to take the two small nuts off holding the black plastic formed block on. Once the block is removed, tape it up so as it can not touch any metal and cause a short. Then take the two small ring connectors that will fit the studs on the back of the alternator and crimp them onto two lengths of wire that will reach from the alternator to the voltage regulator. After crimping the connectors onto the wires, connect one each on the back of the alternator and tighten the nuts back up. Then route the wires from the alternator back to the voltage regulator. Next use your large ring connector and crimp it onto a piece of wire that will reach from your battery to the regulator. Route the wire from the battery to regulator, but DO NOT
hook it up to the battery at this time. Now take one of the wires from the alternator and the wire from the battery and twist them together, then crimp them into one end of the barrel connector. Then take the other end of the barrel connector and crimp it onto the wire from the regulator plug that goes to the TOP
post on the regulator. This is very important, it must be the wire going to the TOP
post or you will pop the regulator. Then take the remaining wire from the plug and the alternator and crimp them together using the other barrel connector.
Now go back and hook the wire onto your battery post. Start your truck and verify that is charging. Put your tools away and go buy yourself another mod since you just saved $800 from not buying a new PCM.