Adding Daytime Running Lights (DRL)

This is a joint posting by Arfur Dent and mikesimp19 with instructions for fitting Daytime Running Lights (from now on referred to as DRL) to a Citroen C3.

MORE WILL FOLLOW A work in progress

The first part of the post deals with the electrical circuit with function to switch the DRL off when the main lights are switched on either by the driver or by the computer as found on some models. The DRL will be on with the 'ignition' - position 3 on the steering lock switch.

An important mention is that all wiring changes should be made with the battery live disconnected, which in itself requires the following of these instructions to help save the BSI from corruption.

The switching control of the DRL is by a new relay, most likely to be sited in the engine bay fuse box which gives easy access to the original wiring and a moisture protected area with a short cable run to the battery earth connection. The engine bay fuse box can be seen in this topic

The parts list appears lower down the page.

This is the wiring diagram for the DRL (click to enlarge). And this is the electronic circuit diagram for the DRL (click to enlarge).
The parts marked F are 3A Fuses

Wire marked A connects to the white wire on PIN 9 of the 16 Way grey connector in the engine bay fuse box and the wire marked B is connected to the grey wire on PIN 15 of the same 16 way grey connector both using blue scotch locks

'A' - PIN 9 and 'B' - PIN 15 are marked in the picture showing the 16 way grey connector in the engine bay fuse box.
Wires to scotch lock connect, shown from a different angle The plug pin numbers are not very clear when looking at the plug in the car, this diagram has the plug pins labelled, ignore the wires, this diagram is about the finding the plug connection numbers. It is possible that the wire colours may be different but the pin numbers will stay the same.
The blue numbers on the diagram, 30, 85, 86, 87 and 87A are also printed on the actual relay to make wiring this up a bit easier . You will need to make crimped spade connections to all the relay pins with exception of 87 as this is not used and should be insulated with a spare insulated spade crimp.


Earth Point
A suitable earth point can be found on the battery negative terminal. The battery negative connection has a threaded bolt able to accept a Yellow ring crimp - 8mm.

If you have multiple wires to connect to earth, use Blue 8mm ring crimp. Blue crimps will take up to 1.1mm to 2.6mm² or 16-14awg cable, more cables, or larger cables will require the yellow crimp that can take about 4.0-6.0mm or 12-10awg cable.
Give the bolt a clean up with some brake cleaner or whatever you have to hand, before attaching the crimp ring with its wire(s). Coat the terminals with battery grease when the connections are nice and tight to prevent future corrosion.

Your decision on how many earths to connect to the battery earth point (negative terminal) would depend on the style of DRL you have purchased. If yours have enough pre-attached cable you can run all the earth cables back to the battery. If you have limited cable attached or no pre-attached cable, an efficient use of copper would be to run one of each 87A wire and Earth to the bumper and then 'tee off' to each DLR behind the bumper. Connect up multiple DLR in parallel (+ to + and - to -). Don't link them in series (+ to - and + to -).


The wire marked 87A is the relay output to your DRL. This needs to be connected to the 'live' or +12v connection on your DRL or the red wire that came attached to your DRL. Multiple DRL units can be linked together 'in parallel', that is multiple DRL can be added by just connecting more units to the earth point and 87A point.


Parts List
The Relay (5 pin, 12v)

The relay doesn't need to carry lots of current as DRL are usually LED powered and this relay will carry the current of multiple DRL quite comfortably.

Two fuse holders, one for the white wire and one for the grey wire....

....with their associated 3A mini fuses. This pack of five, gives you three spare fuses. Don't cut corners by omitting the fuses.

Blue Crimp Connectors (male and female). The female crimps attach to the relay pins, male and female can be used to extend cables and connect the fuse holders. You may need some other crimps depending on what is attached to your DRL.


You may require some Cable in a choice of colours, from eBay. The choice of colour is up to you
More or less cable is required depending on the number of DRL, their location and if they come pre-wired with enough to reach the fusebox.

Tapping into Citroen wiring in the fuse box for PIN 15 and PIN 9 (A and B) can be completed with some Scotch Lock connectors - blue. Or some posi tap connectors if you can find them.


The most important tool for this job, and any other job that requires the joining of wires is the ratchet crimp tool, don't skimp on these and use the inferior pressed steel type instead because you may come to regret it later.

and the most important purchase has to be the DRL themselves, a huge choice available, have a browse through this selection.




A rule of thumb for crimp sizes for cable size, different manufacturers can have slightly different sizes so its always good to have a selection of crimp sizes.

Red Connectors: 0.4mm to 1mm² / 22-16 awg cable
Blue Connectors: 1.1mm to 2.6mm² / 16-14 awg cable
Yellow Connectors: 2.5mm to 6.5mm² / 12-10 awg cable
Two 1mm cables twisted together will require a blue crimp, one 1.5mm cable will require a blue crimp.
There is 1mm cable in various colours on ebay.
This links to a video showing some tips on making successful crimps

It is important spade connectors are of the insulated type. Insulated (use these).