Daylight Running Lights (DRL)

„Daytime Running Light“, or „Tagfahrlicht“ in german.

Daylight running lights can be found in multiple variants. They are using to make a vehicle more visible to incoming traffic. The Mondeo Mk4 Facelift comes equipped with a special LED light installed under the main headlamps.

In this Wikipedia article, many interesting details can be found about this subject.

The DRL unit can be in any of the following three operating states:

  1. Off
  2. Dimmed to approximately 20% luminosity
  3. Undimmed at 100% luminosity

Selection of one of these operating states depends on the following conditions:

  • Ignition state (on, off, engine start, engine stop)
  • Headlights switch position (on, off or automatic. Parking light off, left on or right on)
  • Vehicle status (vehicle is locked, vehicle is open, vehicle is being opened, vehicle is being locked)

The following table provides a matrix relating the possible states that trigger the switching of the DRL:

Vehicle's operating condition DRL state Duration/Condition of DRL state
Vehicle has been locked for a long time Off -
Unlocked (no matter how) Dimmed Approx. 1 minute, off afterwards
Vehicle has been unlocked for at least one minute Off -
Ignition on, motor not started Dimmed Permanently, for as long as the ignition is on
During engine start Off While the started motor is in operation
While driving, main headlights off Fully on -
While driving, main headlights on Dimmed -
Ignition off Off -
Parking light on via activation of the turning signal switch (with ignition off) Dimmed Lift or right DRL
Locked (no matter how) Fully on Approx. 30 seconds, off afterwards

The DRL are composed of three parts:

  1. A plexiglass front cover
  2. A housing frame/support
  3. An electronic board with the control electronics and 4 soldered LEDs

The LEDs used are 4 Osram's „Golden DRAGON“ (type „W5SM“). These LEDs have a beam aperture of 120 degrees, luminosity of about 82 Lumens and a color temperature of 5600 degrees Kelvin.

The electronic circuitry operates by switching a CC. All LEDs are switched together. Dimming is achieved by using PWM and the LEDs themselves. The PWM frequency is 200 Hz (5 ms period), and the pulse duty cycle is 1:16.

In full luminosity mode, the consumption when using 12V voltage input will be of about 520 mA. When dimmed, the consumption will be 45 mA, again at 12V. The LEDs operational voltage range (without impact in luminosity) is 11 to 14 volts. The LEDs start to emit light for input voltages above approximately 6V.

Only one variant can be found in Mondeo Facelift vehicles.

Nevertheless, there are multiple options to retrofit DRL to vehicles without them as a factory installed option, like the Mondeo pre-Facelift. Some of these come integrated as part of new complete headlights assemblies. When doing a retrofit, numerous legal regulations must be observed. Not only the connection and operation are important, but also the location of the newly installed lights is important.

The complete lower front bumper must be removed in this case.

The DRL housing has one 3 pole connector, with the following connections:

  1. GND
  2. +12V for dimmed luminosity
  3. +12V for full luminosity

<image of connector>

Directly connecting a 12V source to pins 2 or 3 should trigger the operation of the corresponding function.

In order to open the DRL housing, it must be heated in an oven. The plexiglass and the mounting frame/base not only are latched together with plastic lugs, but also sealed using adhesive over the entire contact surface.

  1. The allowed light intensity (measured in candela units) according to ECE-R87 (as of June 2010) is at least 400 cd (section 7.1) and a maximum of 1200 cd (section 7.2.2).
  2. The light temperature (measured in degrees Kelvin) according to ECE-R87 is referred to only as „white“. A color temperature of 5500 degrees Kelvin is perceived by the human eye as a brilliant and cold white color.
  • en_discontinued/artikel/tagfahrlicht/start.txt
  • von go4it