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Old 12-09-2012, 06:37 AM   #1
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Join Date: Sep 2012
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Location: York, United Kingdom
What I Drive: 2011 Focus Zetec 1.6

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How to: Install HIDs

This how to is meant to supplement my projector retrofit how to. I DO NOT condone using HIDs in non-retrofitted/reflector headlights.

Bi-Xenon Projector Retrofit:

You will need the following parts and tools:


HID Ballasts
HID Bulbs
HID Relay Harness
50 Watt 6 Ohm Resistors x2 (VERY IMPORTANT, for bulb error messages)


Nuts and bolts
Basic hand tools

NOTE: I’m not sure how North America focus’ computers will react to HID’s but I know that for a fact that my UK focus doesn’t like them. If the car didn’t register the correct current draw from the low beams, it would give me the bulb malfunction beep and message and then cut power to the low beams. So I had to wire in resistors to the circuit to mimic a standard 55w H7 bulb. I now do not have any error messages.

The Relay Harness

First lets start with the relay harness. The standard relay harness is used to reduce the load on the factory wiring. I believe HID's require a higher current in order to ignite and this, over time, can cause harm to the factory wiring. Or at least cause some blown fuses. Imagine you are driving on a dark highway miles away from home. If for whatever reason your HID's cause your fuse to blow, you'll be without headlights until you can change that fuse. A relay harness will also give your HIDs a more constant current as it is coming directly from the battery. I'm not going to go into how a relay works, but if you are interested:

The standard relay harness has the following inputs and outputs

1x 12v Power - Battery +ve
1x Trigger - Factory low beam
2x Ground - Chassis

2x HID Ballasts

The 12v Power connects to the positive post of the battery
The Trigger connects to the factory low beam wiring. (Where the bulb connects)
The Grounds connect to any metal part of the chasis.
The 2 outputs to the ballasts connect to... well the ballasts.

The following diagrams are how it should be laid out in the car. Go hook up the red wire of the relay to the postive battery post, then position the rest of the relay harness behind the respective headlights.

The Ballast

There is a good spot to mount the ballast on the bottom of the headlight. This is where Ford mounts the ballasts for focus' that have HID from the factory. Only slim ballasts will fit here. You may have to cut some of the raised edges to allow for the wires to pass through.

The Bulbs

FOR EURO FOCUS': *At this point if you are installing HIDs onto a reflector, you will need to get some sort of H7 adapter thing to hold the HID bulbs in the reflector as the factory mount will not work. Well actually you could potentially drill a hole through the middle to accommodate the HID bulb and still retain its locking mechanism.*

FOR NORTH AMERICAN FOCUS' *If you are installing HID's into a reflector, you will just need to plug the H11 bulb into the reflector.*

So the HID bulbs look like this. Green represents the components of the trigger. Blue is the bulbs connection to the ballast.

You must connect the two male spade connectors to the factory bulb connections. Below is a picture with the said connections marked in red. You can simply pull the wires out of that black locking mechanism and out comes the female spade connector. Easy.

Note: All the ground wires in the headlight housing are daisy chained together. So the singular wire going to the low beam locking mechanism is the positive wire.

Install the bulbs into your projectors. (Or if you must, your reflectors) Cut a hole in the rubber cap that covers the hole behind the low beam and feed the wires though. Connect the bulb wires to your ballast, and leave the trigger wire dangling out for now.

The Resistor

This is a very important step, do not skip this. You will regret it later if you do. These resistors are really cheap like 5 dollars for a pair on ebay. They are '50 watt 6 ohm resistors'. There is no need to buy expensive 'HID Canbus Decoders' off ebay, because these are the same thing, just not packaged as nicely.

Don't be fooled by the colour of the wire, it doesn't matter which end is connected to where.

One end of the resistor is connected to the chassis.
Other end is spliced to the postive wire of the trigger. (a.k.a. the positive wire going to the low beam)

Making the connections

Time to connect everything up and test it out.


Mount the resistor onto metal, you don't want this burning through anything as they do get hot. A good place to mount this is just underneath where the headlight bolts to the side of the car.

Ground both the resistor and the ground on the relay harness. I grounded and mounted the resistor in the same place.

Connect the ballast to the relay harness


Mount and ground the resistor and harness in the same place on the left side.

Connect the ballast to the relay harness

Connect the trigger wire from the headlight to the relay harness.
(I know I said to make a trigger wire on both sides. This wasn't necessary only the left side needed one, but its good to have another one incase something happens to the other.)

Now, go into your car and turn on your headlights!

Last edited by Chickenmuffn; 12-10-2012 at 07:41 PM.
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