Voltage is available at all times to the headlamp switch from the LIGHTING MaxiFuse® through CKT 42 (RED). Within the headlamp and panel dimmer switch is a 17A circuit breaker which resets automatically. The circuit breaker opens upon heating due to an overcurrent condition. With the circuit breaker open, current stops, and the circuit breaker's thermal element cools. When sufficiently cooled, the circuit breaker closes.

The three-position headlamp switch has the following positions:

When the switch is in the HEADLAMPS position, voltage is available on CKT 10 (YEL) to the headlamp switch. The headlamp switch is part of the multifunction switch on the steering column. By pulling the multifunction switch lever up along the axis of the steering column, the switch changes selections. Repeated switch operations alternate between the high beam selection and the low beam selection.

With the selection of the low beams, voltage is available on CKT 12 (TAN) to the low beam connector pins, or to the low beam headlamps on vehicles with composite headlamps. Because the headlamps are grounded, current flows through the low beam filaments. Then the headlamps emit light.

With the selection of high beams, voltage is available on CKT 11 (LT GRN) to the high beam connector pins, or to the high beam headlamps in vehicles with composite headlamps. Because the headlamps are grounded, the lamps operate.

CKT 11 (LT GRN) also makes high beam voltage available at the instrument cluster for the lighting of the blue headlamp high beam indicator lamp. Since CKT 451 (BLK) grounds the instrument cluster's lamp circuits at ground G103 or ground G104, the lamp lights when voltage is available.