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How to Fit Daytime Running Lights to your car

Philips DaylightGuide DRLs

Philips DayLightGuide daytime running lights are smart, high performance and easy enough to fit (click to see)Daytime running lights (DRLs) are standard-issue on all modern cars, but the idea originally hails from Scandinavia where ambient light levels can be lower all year round – not always so dark that headlights are needed, but gloomy enough to warrant something brighter than sidelights.

Away from the cities, Britain has a lot of countryside similar to Sweden’s – sparsely populated rural areas, woodlands and fast empty rural roads – places where cars can become almost invisible to oncoming traffic against a backdrop of trees, hedges or open countryside, and this poor visibility and contrast is a constant cause of collisions and near-misses. Daytime running lights improve safety by highlighting the presence of vehicles in locations like these, but it took decades for the principle of DRLs to catch on across the rest of Europe. The first car in England to have always-on daytime running lights was Sweden’s Volvo 240 and the British Government also flirted unsuccessfully with so-called ‘dim-dip’ lights for a few years.

Daytime running lights project an intense pencil-beam of light forwards, which shines directly at oncoming traffic and can typically be seen from half a mile away or more.  This has to be more effective than dipped headlights which shine downwards onto the road ahead.

DRLs can be of great benefit during Britain’s winter months, when the sun is low and roadside trees and hedges cast shadows onto country lanes – just like they do in Sweden. Cars tend to hop unseen in and out of shadows and can easily be overlooked by oncoming traffic, and at busier junctions, DRLs are the first thing that other motorists see, forcing them to think twice before pulling out or overtaking.

Daytime running lights turn on automatically with the engine, but they’re not designed for night-time illumination as they would dazzle road users. So they must either dim or switch off at night-times. Some latest ones dim automatically when ambient light levels fall.

Best choice of DRLs

If you don’t have a new car, you can have the next-best thing and benefit from this excellent safety feature as after-market DRLs are readily available as DIY accessories. My advice is to avoid the cheapest ones that are low-intensity and pretty feeble in construction, a bit flimsy or they shine an odd blue-white colour: I think the cheapest ones are just a waste of money.

I chose to fit the latest generation Philips DayLightGuide LED daytime running lights and below I’ll explain  how they are installed. They are intense super-white LED lights made to the highest OEM standard, in robust diecast alloy lamp units with tough gravel-resistant lenses. They are simple to fit (3 wires, 4 at most). Other high-quality types are made by Osram and Hella, some having individual dot-lamps or faceplates that fit your model of car directly, but they can be pretty complex to install as a DIY job, needing relays and extra wiring.

The latest Philips DRL has another neat design feature: their Luxeon LEDs produce a diffused white bar of light rather than individual ‘pixels’ of light, which creates a smart high-tech effect. They go dim when the sidelights are switched on (see later) and they are compatible with hybrid/ stop-start cars too. As a bonus, the Philips DRLs have a ‘see-you-home’ feature so they stay lit for a short time after switching off the engine, to light up your way to the door.

The lamps in this Philips design, like its predecessors, have U-shaped sprung-metal mounting brackets to affix them to your car.  You can screw them directly to the front of your car, or (as in my case) on the underside of the front bumper instead. They can also be fitted in a grille or securely bolted to the front via the two M5 blind holes on the rear of the lights.


Philips DRL DIY Installation hints and tips

Check over the front of your car to decide the best mounting points. It’s a good idea to make two cardboard templates of your LED lights then tape them to the car, to double-check the positioning and mark out the drilling holes.

It’s critical to measure up correctly, and per UK/ EU law Philips cites a minimum of 600mm between the lamps (as a guide, that leaves a minimum 40mm gap either side of a typical front number plate). Some larger DRL light units might prove too big for your car: depending where you fit them there might be insufficient distance left between them. The Philips DayLightGuide is relatively compact and they include a diagram showing minimum and maximum dimensions reference the height above the road surface, edge of the car and distance from the indicator bulbs.

Also important is to check the forwards alignment to ensure the lamps are facing front as uniformly as possible, otherwise oncoming road users will see one lamp glowing brighter than the other.

Module fitted to the inner wing; the two connections are also shown (click to see)The Philips DayLightGuide system has a small control module with generous wires connecting the LED lights via two water-resistant connectors. One lead is 2m long and the other 3m long, enough for a larger car or 4x4. I screwed the module onto the inner wing in the engine bay, not too far from the battery: a tough job needing a power drill and HSS drill bit, then an impact driver to screw the self tappers down. Ensure no pipes or wires are in the way underneath! Others have used strong double-sided pads or tiewraps instead.

After locating both lighting brackets underneath my bumper and drilling small pilot holes into the (plastic) bodywork, they were screwed in firmly using the self-tapping screws supplied. I added a washer or two under the self-tappers to level the lights up, as they would otherwise 'droop' due to the curved bumper design. Both wires were then routed from the control unit and out to the lamps. I routed one carefully around the radiator grille to avoid any drive belts, pulleys and hot exhausts or hoses etc. and the other wire went straight down to the DRL below. I securely bundled up excess wires using tie-wraps as necessary on the car’s existing wires and cables.


Electrical testing and hook-up

The red + terminal wire connects to the +12V battery post, under the head of the clamp's boltThe +12V feed wire has an inline blade fuseholder which can be connected direct to the car battery +12V post. I loosened the + battery terminal’s nut & bolt while keeping the battery connected, cleaned it up with degreaser etc, then I slipped the red wire forked terminal underneath the bolt head and re-tightened it. The negative wire connects to the – battery post the same way.

(Tip: ensure you have your car radio/ CD code number available in case you accidentally disconnect the battery!)

Next, find the nearest sidelight bulb ‘live’ 12V wire (don’t confuse it with the bulb’s earth lead): check the sidelight bulb terminals with a d.c. tester or voltmeter with test probes, and find which wire goes ’live’ when the sidelights turn on.

Digital multimeters are very cheap these days. If you’ve never used a multimeter before, you must select a ‘V’ (Volts, say 20V) range NOT ‘A’ (current). The 0V (black) negative probe of your voltmeter is touched to the car chassis (eg a mounting bolt or screw somewhere) and the + (red) test lead is touched to either sidelight pin, to show which pin goes ‘live’ when the sidelights are on. Practise on a headlight bulb connector if you like.

Scotchlok connection taps into the live sidelight wire; dummy resistor bulb shown (see text) (click to see)A Scotchlok connector (supplied) then splices into the live sidelight feed: the wire runs right through the Scotchlok while the (orange) wire from the Philips module is placed alongside into it, and the connector is closed with pliers to tap into the wiring. The Scotchlok slices into the insulation and makes contact with the copper wire inside.

A fourth wire (blue) on the Philips module is for use on hybrid or stop/ start cars, and for expert users it goes to terminal KL15 (Ignition 2 position) or ACC of the fusebox.  In my case, I left it disconnected. Their diagram shows the unused wire connected to earth, but I found it made no difference.

As these DRLs go DIM when sidelights are turned on, they also replace your existing sidelights. As it’s illegal to show four sidelights, Philips includes two dummy power resistors that replace your existing sidelight bulbs (see photo). I guess this avoids errors arising in CANBUS or high-tech diagnostics that my car doesn’t have anyway.

Testing and finishing off

Do not click the light units into their brackets just yet.  Connect the two lamps to the module and check they work as follows. Turn your sidelights on, and both DRLs should glow in sidelight mode. Turn them OFF again, and your DRLs should now glow at maximum brightness (see-you-home mode) for about 30 seconds before they switch themselves off completely.

DRL in action - note the neat 'striplight' effect of these Philips DayLightGuide LED lamps (click to see)

With the lights still OFF, start the car and the DRLs should come on automatically at full brightness (DRL mode). Turn the engine off and they should extinguish after 30 seconds or so. Only when you are 100% satisfied everything works, click the LED units fully home into their brackets (same way up for both lamps).

Finish off by double-checking and tidying the wiring with tie wraps to ensure nothing will chafe or catch on any engine parts.

Fitting these Philips DayLightGuide daytime running lights has been a very reassuring move and is probably the best money you can spend on an older car. You do feel safer in the knowledge that oncoming traffic can't fail to see you. On quite a few occasions my DRLs have caused oncoming or merging traffic to hesitate or hold back, and I’m sure that on two or three occasions they prevented an accident or near-miss. I wouldn't be without them.


Reader Comments (2)

Thanks for documenting your install. I'm adding these to my car and read your article to prep.

I'm confident I'll sort the wiring details, but if you have a strong opinion on installing similar aftermarket Philips DRLs on a car with existing daytime running lights, I would be grateful for your thoughts. I could do a similar install as yours, or tap into the existing DRL circuit, or an unused ACC port.

In case you're wondering about the motivation to add a second sit of DRLs, it's simple. The OE units are halogen and very dim.


July 1, 2016 at 1:43 | Unregistered CommenterSTK


That's an interesting question that I haven't thought about before,

I don't know what the car lighting laws are where you are, but UK/ EU rules state the minimum distance between DRLs, minimum and maximum heights and distance inboard from the extreme edge of the car.

There are also clear laws about not showing them at night (they must dim or turn off). Philips states that (UK) you can't have more than two sidelights showing at night. Dimmed DRLs might count as four sidelight units which would make them illegal. You might have to disable existing halogen DRLs.

Fitting dimensions as per diagram shown on Conrad:

You might consider using chains of separate dot-lights such as Hella's which I show on my web page.

My personal choice of brands would be Philips, Osram or Hella.

Alan W

July 1, 2016 at 12:59 | Registered CommenterAlan W

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