charging system blues
Mike this post of yours was delayed on showing on my screen...
... this all started at a cruise one eve when a few mopar bums told us headlights seemed dim, ammeter showed system was chg & dischg according to rpm, this indicated to me system was operating as it should
Basically correct.
Here's the deal. The lights get dim because the alternator is not keeping up with demand at idle. So instead of running on the alternator, the car is running on battery.
Yes if you see the battery discharging at idle, then the alternator should charge it when the rpm go up. If you idle this car for long periods of time with the headlights on, its going to drain the battery. This is because the alternator is not getting enough power to all the circuits at idle rpm.
This is common on older vehicles for a combination of two reasons:
a. Oxidation, and sometimes loose or poor connections.
b. Base model alternators produced just enough power at idle to run the ignition and one or two accessories (wipers or lights). This wasn't a problem when the wiring was in brand new condition and the car wasn't idling for longer than a normal traffic light. As soon as the car was moving, the alternator recharged the battery.
Anyway, start with a good voltmeter and clean all of the connections. If the ammeter shows the car running on battery with no accessories on, that's not the way it should be.