For 1990-2009 cars

The headlamps and exterior lamps are controlled by the daytime running lamps (DRL) control module and the light switch/dimmer switch. When the light switch is turned to HEAD and the dimmer switch is in LOW, a ground signal is provided to the DRL control module. The module then provides a ground path to the coils of the head relay and DRL relay. Since the head relay is provided with battery voltage to both the contacts and the coil, the coil becomes energized and closes the contacts providing voltage to the dimmer relay, through the DRL fuse to the DRL relay and through both head fuses (LH-LWR and RH-LWR) to both LH and RH low beam lamps. With voltage and ground provided to the coil of the DRL relay, the coil becomes energized and closes the contacts providing a direct path to ground for both headlamps through SP254 to G103. With voltage and ground provided, the low beam lamps light.

With the dimmer switch in the high position, ground is provided to the DRL control module through the dimmer switch and splice pack 250 to G203. With voltage applied at all times through the dome fuse to the DRL control module and ground is provided through SP261 and SP254 to G103, the DRL control module provides a ground to the coil of the dimmer relay. Since voltage is being applied to the dimmer relay coil, it becomes energized. Voltage is then applied through the closed contacts of the dimmer relay and the head fuses (LH-UPR) and (RH-UPR) to the high beam lamps in the headlamps. Since ground is provided to the headlamps through the closed contacts of the energized DRL relay and SP254 to G103, the high beam lamps light.

The operation of the headlamps with the dimmer switch in pass is similar to the operation of the dimmer switch in the high position, as mentioned in the previous paragraph, with the exception that 2 ground paths are provided to the DRL control module. One path is through junction block 1, the dimmer switch and SP250 to G203, which simulates the operation of the light switch in the head position. The other is through the dimmer switch and SP250 to G203.