a. 12 V with engine off is not fully charged
b. Voltage readings are dependent upon where the leads connect.
c. If this is a dash gage, then it would seem your wiring has been modified.
d. Include all the information about the car's electrical system. A '65 is not the same as '75, a '73 Dart equiped originally equiped with high output alternator and rear window defrost is not the same as a Charger, etc. Then what changes or repairs have been made.
