Headlights (USA)

Exterior Lights

How the Headlights (USA) Circuit Works

High and Low Beams
The headlight relays receive battery voltage at all times. When the headlight switch is turned to the HEAD position, ground is provided through the BLU/GRN wire to the coils of the headlight relays. The relays are then energized, applying battery voltage to the left and right headlights through fuses 43 and 45. The low beam bulbs come on because they are individually grounded by G301 and G201. With the low beams already on, pulling the dimmer switch to HIGH energizes the dimmer relay. When energized, the dimmer relay provides a path to ground for the high beam bulbs and the high beam indicator.

Flash-to-Pass
When the Flash-to-Pass switch is held in the ON position, ground is provided through the BLU/GRN wire to the coils of the headlight relays. The relays are then energized, applying battery voltage to the left and right headlights through fuses 43 and 45. The low beam bulbs come on because they are individually grounded by G301 and G201. With the flash-to-pass switch in ON, ground is provided to the dimmer relay coil. The dimmer relay is then energized, which provides a path to ground for the high beam bulbs and the high beam indicator.

Automatic Lighting
The automatic lighting control unit receives battery voltage through fuse 13 (in the passenger's under-dash fuse/relay box) at all times and receives battery voltage through fuse 9 (in the driver's under-dash fuse/relay box) with the ignition switch in ON (II) or START (III). When the ignition switch is turned to ON (II), the automatic lighting control unit receives an "ignition on" signal through fuse 4 (in the driver's under-dash fuse/relay box).

The headlight relays receive battery voltage at all times. When the headlight switch is in the AUTO position, a path to ground through the headlight switch is removed from the automatic lighting control unit. When the automatic lighting control unit fails to receive this ground signal, it obtains information from the automatic lighting control sensor. When the automatic lighting control sensor detects low ambient light, the automatic lighting control unit provides ground through the BLU/GRN wire to the coils of the headlight relays. The relays are then energized, applying battery voltage to the left and right headlights through fuses 43 and 45. The low beam bulbs come on because they are individually grounded by G301 and G201. With the low beams already on, pulling the dimmer switch to HIGH energizes the dimmer relay. When energized, the dimmer relay provides a path to ground for the high beam bulbs and the high beam indicator.

When the driver's door is open, ground is provided to the automatic lighting control unit through the GRN/ORN wire. When the automatic lighting control unit receives this ground signal, it removes ground from the coils of the headlight relays and causes the headlights to turn off. The automatic lighting control unit will also turn off the headlights if the ambient light levels rise to daylight conditions.