Headlights/Daytime Running Lights (DRL) Circuit Description Pontiac Domestic
The daytime running lamps (DRL) module is designed to automatically turn on
the low beam headlamps and the front park/turn lamps when the ignitionswitch is
in the RUN position, the headlamps are off, and the park brakeis off. There
is no ambient light sensor. It is replaced by a jumper.
The DRL module will not operate any headlamps or exterior lamps if the park
brake is applied before the ignition switch is turned tothe RUN position. This
allows the driver to start the vehicle and keepthe headlamps off, as long as
the park brake is applied. The DRL moduleactivates the headlamps when the park
brake is released with the ignitionswitch in the RUN position. The headlamps
will not turn off if the parkbrake is applied after the ignition switch is turned
to the RUN position.
When the headlamp switch is turned to the PARK or HEAD position, the DRL module
turns the front park/turn lamps off. When the headlampswitch is turned to the
HEAD position, battery voltage is applied to the low beamheadlamps. Battery voltage
is also applied tothe headlamp dimmer switch. When the headlamp dimmer switch
is turned to high beam, voltage is now applied to both high beam headlamps. The
low beam headlamps stay onwhen the headlampdimmer switch is in the high beam
position. When theheadlamp dimmer switchis in the high beam position, the instrument
clusterhigh beam indicator turns on.
Headlights/Daytime Running Lights (DRL) Circuit Description Chevy Dom, Pont Can, and Gulf States
The DRL module does not operate if the system voltage is less than 9 volts
or greater than 18 volts.
The daytime running lamps (DRL) module is designed to automatically operate
the front park/turn lamps and the low beam headlamps depending ontheoutside
light conditions.
The DRL module operates in 2 modes:
| | In the day mode, the DRL module turns on the turn lamps when the
DRL ambient light sensordetects daylight under the following conditions: |
| - | The ignition switch is in the RUN position. |
| - | The headlamp switch is off. |
| - | The park brake switch is off. |
| | In the low light mode, the DRL ambient light sensor detects darkness, turning
on the low beam headlamps (to full intensity) and the turn lamps. |
| | Additionally, the DRL ambient light sensor turns on the following lamps: |
| - | The tail/stop lamps (Chevrolet) |
| - | The tail/stop/turn lamps |
If the engine stalls with the DRL module in the low light mode, the DRL module
turns off the low beam headlamps and the turn lamps while the engineis being
cranked. The DRL module turns on the following lamps whilethe engine
is being cranked:
| • | The tail/stop lamps (Chevrolet) |
| • | The tail/stop/turn lamps |
Pontiac Canada
When the headlamp switch is turned to the PARK or HEAD position, the DRL module
turns the front turn lamps off. When the headlamps are turned onby the headlamp
switch, battery voltage is applied to the low beam headlamps. Battery voltage is also
applied to the headlampdimmer switch. When the headlamp dimmer switchis turned
to high beam, battery voltageis now applied to both high beam headlamps. The
low beam headlamps stay on when the headlamp dimmer switch is in the high beam
position. Whenthe headlamp dimmer switch is in the high beam position, the instrument
cluster high beam indicator turns on.
Chevrolet
When the headlamp switch is turned to the PARK or HEAD position, battery voltage
is applied to the headlamp dimmer switch. Whenthe headlamp dimmer switch is
in the low beam position, battery voltageis applied to the low beam headlamps.
When the headlampdimmer switch is moved to the high beam position, the low
beam headlamps turn off. Voltage is now applied tothe high beam headlamps, and
the instrumentcluster high beam indicator turns on.
Daytime Running Lamps (DRL) Ambient Light Sensor
The DRL ambient light sensor is a light sensitive variable resistor. The resistor
of the DRL ambient light sensor decreases as the outside lightintensity increases.
The DRL module performs the following functions:
| • | Measures the voltage drop across the DRL ambient light sensor. |
| • | Determines whether the DRL ambient light sensor should operate in the
day mode or the low light mode. |
Park Brake Input
The DRL 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 driver to start the vehicle and keep the headlamps off, aslong as
the park brake is applied. The DRL module activates the headlampswhen the park
brake is released with the ignition switch in the RUN position.The headlamps
will not turn off if the park brake is applied after theignition switch is turned
to the RUN position.
Headlights/Daytime Running Lights (DRL) Circuit Description Scandinavia
When the ignition switch is turned to the RUN position, battery voltage is supplied
from the TURN B/U Fuse 2 tothe headlamp switch and the DRL relay. Voltage is
then applied at all times (when theignition switch is in RUN) to the exterior
lights. The LH positioning lamp, the license lamps, the RH side marker lamps,
the tail lamps, and the tail/stop lamps turn onand stay on.
When the ignition switch is in the RUN positionthe DRL relay is energized.
Voltage is applied to the low beam headlamps with the switch closed, turning the
low beam headlampson.
When the headlamp switch is moved from OFF to HEAD, voltage is no longer applied
to the DRL relay. Voltage is now supplied to turn the high beam or the low beam headlamps
on.
When the headlamp dimmer switch is in the high beam position, voltage is applied
to the instrument cluster, turning the high beam indicator on.
