Headlamp: Description and Operation

The headlamps may be turned on in 3 different ways. First, when the headlamp switch is placed in the ON position, for normal operation. Second, with the twilight switch placed in the ON position, for automatic lamp control (ALC). And third, with the twilight switch placed in the ON position, with the windshield wipers ON in daylight conditions, after a 6 second delay. During ALC control the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. The LCM provides battery positive voltage to the signal circuits of the headlamp switch. The signal circuits include the headlamp on input, the Flash-To-Pass feature, and the high beam input.

The lamp control module (LCM) provides battery positive voltage to the signal circuits of the headlamp switch. The signal circuits include the headlamp input, the Flash-To-Pass feature, and the high beam input. When the headlamp switch is ON, a ground path is available for the headlamp switch signal circuit of the LCM through the headlamp switch. The LCM provides battery voltage to the low beam circuit or of the high beam circuit, if the headlamps are necessary. The position of the headlamp high beam dimmer switch determines which circuit has battery voltage. When the low beam circuit is energized, current flow goes to both low beam fuses. Current flows to the low beam headlamps. The headlamps have ground at G105 and at G106. When the high beam circuit is energized, current flow goes to both high beam fuses. Current flows to the high beam headlamps. The current flow of the left high beam is from the fuse to the left high beam lamp. From the lamp, the current flows to G106 W/T62 or the LCM W/O T62. The current flow of the right high beam is from the fuse to the right high beam lamp. From the lamp, the current flow is to ground at G401. If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.