How Idiot Lights Work

1957 Chevrolet

How Idiot Lights Work. Generator – Alternator warning lights also known as an idiot light or dashboard indicator light may be the most misunderstood part of the charging system. This light is not just for idiots! It can be a very useful tool when diagnosing charging system problems. When the key is turned on, current flows through the warning lamp, field coils and then to ground causing the lamp to illuminate. Once your engine is running, a higher alternator voltage at the field coils should turn the dashboard lamp off.

When your warning light is ON basically, it means that there is a significant mismatch between the voltage that the charging system is producing and the battery voltage. Low output from the alternator or a broken belt could be the reason for this light to come on. Even with a Voltmeter or Amp meter under the dash, it is a good idea to also have a warning light. Warning lights attract attention immediately. Only with a 3 wire alternator conversion can you make use of a dashboard indicator!


How Idiot Lights Work - 1957 Chevrolet
1957 Chevrolet 150


How Idiot Lights Work - 1957 Chevrolet
1957 Chevrolet 150