Headlamps
Battery voltage is applied to the headlamp switch continuously through
CKT 2340. Voltage is applied to the headlamp dimmer switch and to the
daytime running lamps (DRL) control module through CKT 10, when the
headlamp switch is in the HEAD position. When the daytime running lamp
(DRL) control module receives voltage on CKT 10, it disengages
the DRL function. Battery voltage is applied to the low beam headlamps
through CKT 12 when the headlamp dimmer switch is placed in the
LOW position. Battery voltage is applied to the high beam headlamps and
to the high beam indicator in the instrument cluster when the headlamp
dimmer switch is placed in the HIGH position.
Daytime Running Lamps (DRL)
The DRL control module is designed to automatically operate the exterior
lights depending on the outside light conditions.
The DRL control module operates in the following 2 modes:
| | In the day mode, the DRL ambient light sensor senses daylight then the
DRL control module activates the front turn lamps (non-flashing) under the
following conditions: |
| • | The ignition is in RUN. |
| | In the night mode, the DRL ambient light sensor senses darkness turning
off the front turn lamps and turning on the headlamps through CKT 10. |
| | Also in the night mode, the DRL ambient light sensor activates the following
lamps through CKT 9: |
| • | Voltage is also fed back through CKT 9 to the headlamp
switch assembly to control IP dimming. |
If the engine should stall with the DRL control module in the night
mode, the DRL control module will turn off the headlamps, leaving the side
marker, park, license and tail lamps in the ON position while the engine
is being cranked. The headlamp and instrument panel lamp dimmer switch
operate as usual.
The DRL control module receives voltage from the DRL Fuse through CKT 1839
and the HVAC/DRL Fuse through CKT 241. The park lamps and/or the headlamps
may be operated manually at any time by using the headlamp and the instrument
panel (IP) lamp dimmer switch. The DRL module will not operate if the
system voltage is less than 9 volts or greater than 18 volts.
Daytime Running Lamps (DRL) Ambient Light Sensor Input
The DRL ambient light sensor is a light sensitive variable resistor.
Its resistance decreases as the outside light intensity increases. The DRL
control module measures the voltage drop across the DRL ambient light sensor
and determines whether it should operate in the day or the night mode.
Park Brake Input
The DRL control module will not operate any headlamps or exterior lamps
if the park brake is applied before the ignition switch is turned to the RUN
position. This allows the operator to start the vehicle and keep the headlamps
off, as long as the park brake is applied. The DRL control module will
activate the headlamps when the park brake is released with the ignition
switch in the RUN position. This feature will only function when the park
brake is applied before the ignition switch is turned to the RUN position.
The headlamps will not turn off if the park brake is applied after the
ignition switch is turned to the RUN position.
