Headlamp: Description and Operation
HEADLAMPS
The headlamps can be used 3 different ways:
- Place the headlamp switch in the HEAD position for normal low and high beam operations
- With the twilight delay switch placed in the ON position for automatic lamp control (ALC).
- With the twilight delay switch in the ON position with the windshield wipers ON in daylight conditions after a 6 second delay.
For normal low beam headlamp operation, ground is applied at all times from G200 to the headlamp switch. When the headlamp switch is placed in the HEAD position, ground is applied through the headlamp switch ON signal circuit to the dash integration module (DIM). The DIM then applies a ground through the headlamp low beam relay control circuit to the headlamp dimmer switch. When the headlamp dimmer switch is in the LOW position ground is then applied through the headlamp dimmer switch to the HDLP LO BM relay in the underhood fuse block. This energizes the relay allowing battery positive voltage to be applied through the HDLOBML and HDLOBMR fuses to both left and right headlamps. The ground for the left headlamp is applied at all times from G103 and the ground for the right headlamp is applied at all times from G401.
For normal high beam headlamp operation, ground is applied at all times from G200 to the headlamp switch. When the headlamp switch is placed in the HEAD position, ground is applied through the headlamp switch ON signal circuit to the DIM. The DIM then applies a ground through the headlamp relay control circuit to the headlamp dimmer switch. When the headlamp dimmer switch is placed in the HIGH position, ground is applied through the headlamp dimmer switch to the HDLP HI BM relay. This energizes the relay and allows battery positive voltage to be applied through the HDHIBML and HDHIBMR fuses to both left and right high beam headlamps. The ground for the left headlamp is applied at all times from G103 and the ground for the right headlamp is applied at all times from G401.
For normal flash to pass operation (FTP), ground is applied at all times from G200 to the headlamp dimmer switch. When the headlamp dimmer switch is placed in the FTP position, ground is applied through the headlamp dimmer switch to the FTP input of the DIM. The DIM then applies a ground to the HDLP HI BM relay through the headlamp high beam relay control circuit. This energizes the relay and allows battery positive voltage to be applied through the HDHIBML and HDHIBMR fuses to both left and right high beam headlamps. The ground for the left headlamp is applied at all times from G103 and the ground for the right headlamp is applied at all times from G401. The high beams will be on as long as the switch is held in the FTP position.
During ALC the low beam headlamps will be on at reduced intensity in daytime running lamp (DRL) operation during daylight conditions and low beam headlamps and park lamps on at normal intensity during low light conditions. If the windshield wipers are turned on while the DRL lamps are illuminated, the DIM receives a signal through the lights on with wipers signal circuit. The DIM will then turn on the normal low beam headlamps.