Reply to "Ampere gauge bouncing around"

The questionable design used sends 100% of the alternator's amperage through the amp gauge before it goes anywhere else. If anything in the car draws power, the gauge reacts. The usual fix is to add a 'shunt'- a conductor directly across the amp gauge terminals- that reduces the needle action and acts like a safety valve. The shunt must be insulated for safety, and can be sheet brass or heavy gauge wire; the bigger the conductor, the less needle action and the more current goes thru the shunt. Tune it for the action you prefer...