Here is a simplified diagram from "MyMopar:"
In the diagram below, notice the wire from the IGN switch to the coil ballast, and then off towards the regulator. Notice that a blue and a blue/ white "Y" off to both the regulator and one of the alternator field connections
Turn the key to "run", engine off, and take your meter and probe the blue at the althernator field WHILE IT IS still hooked up.
Stick your other probe on the battery POSITIVE post, set to "low DC volts". You are looking for a VERY low reading, the lower the better. You are measuring the "voltage drop" through the harness from the battery, through the bulkhead connector, through the IGN switch, back out the bulkhead connector, and to the alternator/ regulator.
You DO NOT want to see much over .2V (two TENTHS of a volt.) Much over this, you have a bad connection in the cricuit path mentioned above. Over .5 (1/2 volt) means you REALLY need to look things over. This drop will cause poor regulation as well as over charging.
Next, take a critical look at the regulator CONNECTOR. Is it loose? dirty? corroded? The connections MAY be broken inside the molded connector. You can buy these, last I looked, at NAPA. Work the connector in/ out of the regulator connector to "scrub" the terminals clean, and make sure it fits tight.
Read this article from MAD electric:
which came from here:
Look over the simplified diagram on the page. At LEAST two points in the diagram that are chronic trouble on Mopars is the BULKHEAD CONNECTOR. In particular are the connections for the battery feed and the alternator charging line.
Fire up the engine and run at a fast idle. Check the battery voltage, what is it?
Should be close to 13.8-14.2, in no case below 13.5 and in no case above 15
IF the battery voltage is low, move your meter over to the output stud on the alternator. IF there is more than about 1 volt difference, you have harness/ bulkhead connector/ ammeter circuit problems.
Other problem areas in the bulkhead connector is the blue "ignition run" circuit, and the headlights.