How to wire DRLs
 

In many parts of the world driving with your lights on during the day is mandatory for part or all of the year. Also, many drivers keep their lights on, even if they are not required to, for safety reasons. Unfortunately, the extra electrical load (150-200W) increases fuel consumption.

Daytime running lights, especially LEDs, can provide the same visibility while consuming much less power because:

• They produce only enough light to make the vehicle visible, not to illuminate the whole road ahead,
• Only the DRLs are on, while the position, dashboard, and license plate lights stay off, since they are not needed.

A pair of LED DRLs can use as little as 10 watts. In the Europe, all 2012 model year cars must have OEM fitted DRLs.

So, I've started this thread to help make it easier to install DRLs, especially the from the electrical side, which may be a little tricky. European law says that DRLs must turn on when the key is in the position which allows the engine to be operational (though the engine itself need not be turning), and must turn off when the headlights or high beams turn on (except when only flashing the highbeams). Here is a diagram of how my DRLs are wired to fulfill these requirements, and a few extras:

On the left is an ON-OFF-ON switch, the middle pin gets +12V from the accessories wire (off when engine is off). Position II (AUTO) routes through the relay, which disconnects the DRL when the headlights turn on. Position I (ON) bypasses the relay directly to the DRL, so they do not turn off when the headlights go on.
The LED at the top is mounted in the cabin to let the driver know if the DRLs are lit up.

The bypass is not really needed, but may come in handy (for example as foglights). You may want a way to turn the DRLs off, since there are places where using them is illegal (or at least was a few years ago), for example on highways in Portugal, or in Greece within city limits. I'm not sure if this is still the case, if not then the switch itself (and even the cabin LED) can be omitted for simplicity.

In my cockpit you can see the small LED (not lit) above the I-0-II rocker switch on the right:

Nice diagram!
Are you saying you have to equip your vehicle with DRLs even when it was not factory equipped to conform to the law?

Luckily my car did not come with it. I think here in the US it is illegal to disable the DRLs if the vehicle is factory equipped with it.

Some vehicles use the high beam at a reduced intensity (PWM) for DRL.

My wife's 2000 GMC Jimmy turns off the DRL when the turn signal is used. (might be a fluke but I saw it when she followed me once).

Also here they are hooked up to where there has to be daylight (sensor on dash), the vehicle has to be shifted out of park,and the parking brake can not be set in order for them to come on! Makes it hard to check for one person if looking for a burned out DRL bulb. (I'm only familiar with GM vehicles).

Lastly I love your switches! What are they all?

Barna

No, only new vehicles must have them, but retrofitting older cars is becoming popular.

I described the switches in the cockpit thread.

You should also notice that if you have ksenon headlamps they don`t worn out so much and you don`t have to change the expensive light bulbs so often. Which can be even bigger saving than the electrical load savings ;). Same goes for regular halogens also if your car is so difficult to replace the bulbs that it need to take out the front bumber etc at car service which takes time and costs money.

The EU directive regarding DRL takes priority over national legislation.
You are allowed to fit them if they comply to the directive, and use them in all conditions where regular headlights are not made mandatory, in the entire EU.