GM Headlight Switch Circuit Functions | American Autowire GM Headlight Switch Circuit Functions. GM Headlight Switch Circuit Descriptions: 0. Ground output wire through the rheostat. 1. 12 volt battery unfused feed into H/L switch circuit breaker • Feeds power to #7 when headlight switch is in “Park lights on” position. Chevy Headlight Switch Wiring Diagram | Free Wiring Diagram Assortment of chevy headlight switch wiring diagram. A wiring diagram is a simplified conventional pictorial representation of an electric circuit. It reveals the components of the circuit as simplified forms, as well as the power and signal connections in between the devices.