Daytime Running Lamp: Description and Operation

The Daytime Running Lamps (DRL) (dimmed low beam) illuminate when the ignition is switched on. In addition to the headlamp system, a DRL relay is installed.

Once the ignition is switched on, the components are connected in series:
DRL relay, left-hand low beam bulb, fuse for the left-hand low beam bulb, fuse for the right-hand low beam bulb, right-hand low beam bulb and ground.

By connecting the components in series, the voltage supply to the low beam bulbs is reduced which reduces the power of the low beam.

If the lamp switch is set to 'headlamps', the DRL relay is energized and the DRL resistor is cut.

If the headlamp flasher or the high beam is switched on, the DRL relay engages and switches both low beam bulbs on once more in parallel to make them shine at full power again.

The diodes for the DRL allow the current to flow in one direction only when the lamp switch is switched on.

WARNING: DRL RELAY (R1) GETS VERY HOT DURING OPERATION. BE SURE RELAY HAS COOLED BEFORE HANDLING.

The DRL system is designed to turn the low beam headlamps ON with a reduced light output when the conditions are met:
^ The ignition switch is in the RUN position.
^ The headlamp switch is in the OFF or PARK position.

The DRL system, which is required by the Canadian government for vehicles sold in Canada, contains the following:
^ a relay (R1) located in the Battery Junction Box.
^ wiring connected to the headlamp instrument panel junction wire.
^ the DRL output of rapidly pulsating short bursts of power which cannot be measured by using most multimeters.