Chrysler Repair: 91 5th Ave.: Alternator problem

Question
Hello Roland,

Happy New Year and thanks for your assistance in advance.  

I have a 91 5th ave 3.3.  I am getting a code 12 (battery hasn't been disconnected) and code 41.  I have checked battery, all connections including ground, battery, alternator.  The alt is putting out between 14.3 and 14.5v which I suspect is a bit high.  The voltage across the two field terminals on the alt is 8v and battery voltage on the other.

Any suggestions appreciated.

Thanks
Chris

Answer
Hi Chris,
The 41 is about the alternator field coil circuit and that is fairly straight forward. You could measure the resistance across the field coils (the pins where the dark blue and the dark green wires are connected. The dark blue wire is from the ignition switch and should show battery voltage in the run position. The dark green goes to pin 20 of the pcm and that is the regulator function (switches quickly on and off to ground to establish the 14.3 output). If you are getting that output on the black/gray wire that connects to the battery when you are running the engine then I don't see any problem with the field coil unless it is an intermittent situation. So check out the wires I listed and try erasing the codes by disconnecting the battery briefly and see whether the 41 code reappears or not.
Roland