Jack:
Put a voltage(read multi tester) tester on the battery when the car is running at idle and you should see 13-14 volts. If you don't , suspect the alternator is failing... Take it to an alternator shop and have them go over it and repair it .
If you have over 12.5 volts at idle, don't worry . Look elsewhere...
Ameters are not al that indicative of weak alternators.
Dave