What should the battery gauge read when the engine is not running?
What should the battery gauge read when the engine is not running? A fully charged battery should read about 12.5 volts when the key is in the ignition and turned partially, but the car's engine is not running. Step 2 Look at the voltmeter while the engine is running. Readings of 14 to 14.5 volts on the gauge when as a good sign. Why does the battery gauge go back to 12 volts? When your gauge read ~12volts and a new battery it went back to 15 volts, the old battery was overloading the alternator with an internal short. At...