GM Headlight Switch Circuit Functions | American Autowire 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. • Feeds power to #6 when headlight switch is in “Headlights on” position. 2.