Chrysler Repair: Overvoltage of alternator, codes 41 and 46, plymouth grand voyager, measure resistance

Question
94 plymouth grand voyager SE 3.3L v6 getting codes 41 and 46, charging system too high, replaced alternator, worked for about 10-15 minutes, then right back to charging 18-20 volts. prior to changing alternator, was also charging 18-20 volts, thought it was faulty...having mechanics work on it, but we are not making much headway, any help would be good


Answer
Hi Jeff,
That happens when the voltage regulator function which is accomplished by oscillating on and off the alternator field coil ground wire by the pcm is for some reason not happening.
I have the '93 manual and it says that when you have verified the overvoltage you do the following: Turn off the ignition, then jump a wire from the + post of the battery to the dark green/orange wire post at the alternator (which is called the A142 wire). Then measure the voltage at the dark green wire's post of the alternator (called the K20 wire):
More than 10V, then try to wiggle the wire harness that runs between the alternator and the 60-way plug at the PCM to check for intermittant short. If none found then replace the PCM.
Less than 10V, then disconnect the jumper from the battery to the A142 post. Disconnect the 60 way at the PCM and check for damage/corrosion and if found repair. Reconnect the 60-way and the jumper and recheck the K20 post voltage. Still less than 10V then disconnect jumper and disconnect all wires at the alternator. Then measure resistance of k20 wire to a good ground:
Less than 5 ohms then the k20 wire is shorted to ground and needs to be repaired.
More than 5 ohms then measire whether K20 wire's post itself on the alternator is grounded (when the k20 wire has been removed from it). If the post is grounded then the alternator is faulty because of a permanently grounded field coil.
So those are the possibilities.
Roland