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HID Xenon Light Installation (Classic)

Introduction

If you like the new HID lights on all Subaru’s after around 2006, how about this DIY project to fit them to your Classic. The following article is a comprehensive guide which ended up being published in our SIDC’s TripGrip magazine.

What’s HID and How does it work?

The term HID stands for High Intensity Discharge, which refers to the lighting technology that relies on an electrical charge to ignite xenon gas inside a sealed bulb, unlike a standard bulb that uses a wire filament that heats up and produces light, when 12 volts DC is passed through it.

The HID system creates light by creating an electrical arc between two electrodes in an arc tube. The bulb containing the xenon gas enables the arc to generate a strike. It is the heat produced from this strike that produces a plasma which boosts the intensity of light created by the arc. By supplying a constant current flow at this point that the xenon bulb light output is sustained.

The HID Ballast is used to regulate the flow of current through the xenon bulb. It has to keep a constant current flowing to keep the gas molecules in an excited state to light the HID bulb. The Ballast unit is basically a DC to AC converter, with a constant power output, that has a built in circuit that creates a train of high frequency pulses. The Ballast works in two modes, the first mode is to use these series of pulses at a very high voltage level (5kV to 20kV), this it uses to break down the gas in the bulb, causing it to ionize. Once the gas is ionized it will then be able to conduct an electrical current. With this current now flowing, the Ballast Unit does not need to supply such high voltages and can now reduce its AC output to a far lower level between 70v and 350v.

What’s inside the box…

Now, once you have emptied out all the bits in the box and on to the floor (illustrated below), you get:

1. 2 Ballast Boxes
2. 2 quick release bulbs with holder
3. Relay Control Module and wiring loom
4. Brackets and bolts to attach ballast to chassis
5. Tiewraps to tie down cables in the car

The system components

Ballast Unit

The Ballast Unit is used to convert an incoming 12v to 14v DC supply, to a high voltage AC supply to start and then drive the HID bulbs. It has a two pin input socket on the left (see fig. 1) from the wiring loom, and a moulded twin output lead on the right (see fig. 2) to feed the HID bulbs. Both input and output cables have water proof connectors on them, so when connecting the ballast output leads to the bulb, both connector pairs (Ballast and HID bulb) are keyed for easy identification. (These are constructed using a thick red wire for the positive feed and a thick black wire for the negative feed).

Note: the lead ends to the bulb are made so that they only fit one way

With reference to the Ballast Rear View (see fig. 3) the left side of the unit has the two pin input socket (from the loom). On top of this socket there is a moulded ‘+’ sign to indicate the polarity of the connector when you connect into the loom.

Note: the input lead from the loom can easily be plugged in the opposite way around so be careful not to wire it in the opposite way around.

Fig. 1 Ballast Unit - Top View

Fig. 2 Ballast Unit output lead

Fig. 3 Ballast Unit - Rear View

Xenon Bulbs and Holder

The bulb assembly comes encased in a protective shroud/light deflector (see fig. 4). The bulb assembly then unscrews from the shroud to allow you to get at the bulb. When installing the bulbs, after the standard bulb is removed from the headlamp unit, the shroud is inserted into the headlamp unit where the old H4 bulb was removed from. The shroud emulates the physical bulbs H4 shape (see fig. 7) and provides a secure connection for the HID bulb assembly. The bulb assembly now screws into the shroud, which now acts as a carrier for the delicate HID H4 Xenon bulb.

The bulbs have two pairs of connecting wires (see fig. 5 and 6) the heavier pair that connect to the Ballast Unit and a lighter pair to connect to the Relay Control Unit (to switch high and low beams) via the loom.

Fig. 4 Xenon Bulb and holder

Fig. 5 Xenon Bulb lead ends

Fig. 6 Xenon Bulb lead ends

Fig. 7 Standard H4 Bulb and HID Shroud Orientation

Control Module and Wiring Loom (Left Hand Side)

The brain of this installation is Relay Control Unit (RCU). This unit will take its supply feed from the battery directly via a separate in-line 30 amp fuse. It uses separate earth returns, at the end of each of the two loom, via earth points on the chassis. The RCU also takes an input from the left hand headlamp socket (from the car loom that fed the original bulb) and uses this to sense when the headlamp light is being switched from main beam to high beam. Using this sense input, it then uses an internal switching mechanism to control the low and high beam output on the HID bulb. On the left (and right) loom, there a pair of thinner gauge leads that go to each bulb, these are used to provide this switch control to low and high beam function.

Fig. 8 Control Module and Wiring Loom - Left Hand Side

Fig. 9 Relay Control Unit (Showing wired connections)

Looking at the illustration (See Fig. 8), from left to right in a clockwise direction we have:

1. Relay Control Unit (RCU)
2. Left hand earth-return cable
3. Input DC Supply feed to left hand Ballast (from RCU).
4. Low/High Beam Control feed to left hand HID bulb (from RCU).
5. Low/High Beam Input Sense feed from the cars lighting loom (left hand) socket.
6. Input DC supply feed (fused) to the RCU (from battery).
7. RCU feed to right hand side loom assembly (showing going off the bottom of the picture).

Wiring Loom - Continued (Right Hand Side)

Fig. 10 Wiring Loom - Right Hand Side

Continuing from the previous wiring loom photo, based on the illustration (See Fig.10), we have from left to right in a clockwise direction:

1. Low/High Beam Control feed to right hand HID bulb (from RCU).
2. Input DC Supply feed to right hand Ballast (from RCU).
3. Right hand light earth-return cable.
4. Right hand side loom assembly going back to the RCU.

How it’s all connected together.

The loom is pretty self explanatory and straight forward to fit. It has two input feeds, the first is the DC supply direct from the battery terminals to supply the RCU with the voltages it needs to drive the Ballast Units and the second input feed is to supply the light switching sense, to the RCU, to be able to control the switching of the Low/High HID beams.

The loom then has two cable bundles, one bundle goes to the left side of the car and the second to the right side of the car. This will be routed over and in front of the radiator. The function of these bundles is to provide the wiring required for the Live DC supply voltage to the Ballast Unit and switching control to the HID bulb.

The Ballast Units input connector have a live feed and an earth return (negative). The live cables for both the left and right Ballast Units are shared as they come from the RCU, however the earth returns are independent of each other and the system requires that the earth for the Ballast Units is run back using the cars chassis. It is very important that these chassis connections are made and that the connections are rust, grime and oil free. Failure to follow this may result in low light output or at worst no light output. The loom cabling carries no earth return wiring for the Ballast Units or the switching control to the HID bulb, only live connections.

RCU Supply Feed

The first feed is a +12v supply to be taken from the battery positive terminal (See Fig. 11). This has its own in-line fuse for protection purposes, due to the higher start-up currents involved when the lights are initially turned on. This feed supplies the RCU which controls the rest of the system.

Fig. 11 Live DC supply from battery terminal

Note: As the power supply cable is approximately 65cm in length the RCU will have to be positioned on the left side of the car.

RCU Light Sensing Feed

The second feed to the RCU is a 3 pin plug which is used to connect into the cars lighting loom connector. The RCU uses this feed, to sense when the Low/High beams are selected, to control the HID Low/High Beam switching.

Looking at the illustration (See Fig. 12) is the left hand connections on the loom, the very left hand connector is the 3 pin H4 connector, this connects directly into the socket on the loom on the car that should connect to the left hand headlamp. (The right hand socket on the cars loom for the right hand headlamp can be wrapped and tied up out of the way - this is because only one sense input is required, the RCU now controls the low and high beam switching from this point).

Note: This 3 pin plug must connect to the left hand lighting connector on the cars wiring loom (due to location of the battery)

Left Hand Side RCU Loom

Fig. 12 Left Hand Side Loom Input Wiring

Fig. 13 Earth return lead and connector

Fig. 14 Earth return chassis connection point

Looking at the illustration (see Fig. 12) we have the left hand side loom wiring showing (from left to right):

1. RCU Low/High sense input feed to connect to the left hand headlamp connector.
2. RCU Low/High switching feed (thinner gauge wires) to connect to left hand HID bulb.
3. Left hand DC supply feed (thicker gauge wires) to connect to the left hand Ballast.
4. Also attached to this part of the loom, (See Fig.13) is the earth return lead.

Illustrated above (See Fig. 14) is an earth point behind the left hand headlamp that will be used for this earth return.

Right Hand Side RCU Loom

Fig. 13 Earth return lead and connector

Fig. 15 Right Hand Side Loom Input Wiring

Fig. 16 Earth return chassis connection point

Looking at the illustration (See Fig. 15) we have the right hand side loom wiring showing (from left to right):

1. Right hand DC supply feed (thicker gauge wires) to connect to the right hand Ballast.
2. RCU Low/High switching feed (thinner gauge wires) to connect to the right hand HID bulb.
3. Also attached to this part of the loom, (See Fig.13) is the earth return lead.

Illustrated above (See Fig. 16) is an earth point behind the right hand headlamp that will be used for this earth return.

Ballast Unit Outputs

The Ballast Unit output for each side is made using a thicker gauge/heavy duty twin wire lead (See Fig.17), coloured red and black with waterproofed. moulded and keyed connectors. These attach to the HID bulbs with their opposing connectors (See Figs 18,19 & 20), so basically red to red and black to black. Even if you had to do this in poor light there is no way that they could be wired the wrong way around as the connectors are totally different in their size and construction.

Fig. 17 Ballast lead ends

Fig. 18 Right hand Ballast to bulb wiring

Fig. 19 Xenon Bulb lead ends - Top

Fig. 20 Xenon Bulb lead ends - Front

Getting it all into the car

Pre install light height/level check

Right sidelight and headlamp removal

We need to remove the sidelight first, there is a single screw joining the sidelight to the headlamp (See Fig. 21). Remove this screw and then pull the sidelight forward and out. Remove the sidelight bulb and holder by turning the bulb holder anticlockwise. With the sidelight removed there are two 10mm bolts that hold the headlamp in place, remove these bolts (see Fig.22). In order to get the headlamp out there are two more 10 mm bolts that hold it in from the front. To get to these you need to remove the front grill by pushing down on the release clip that side in the hole on the top of the grill(See Fig. 23). Use a small flat tipped screw driver to push down on the clip and gently pull on the grill. Once the grill is off then remove the two remaining 10mm bolts. Remove the headlamp loom connector from the headlamp and pull out the headlight.

Fig. 21 Right Sidelight Screw

Fig. 22 Right Headlamp 10mm Bolts - side

Fig. 22 Right side front grill release

Fig. 24 Right Headlamp 10mm Bolts - front

Left sidelight and headlamp removal

Again we need to remove the sidelight first, there is a single screw joining the sidelight to the headlamp (See Fig. 24). Remove this screw and then pull the sidelight forward and out. Remove the sidelight bulb and holder by turning the bulb holder anticlockwise. With the sidelight removed there are two 10mm bolts that hold the headlamp in place, remove these bolts (see Fig.25). In order to get the headlamp out there are two more 10 mm bolts that hold it in from the front, remove these two remaining 10mm bolts. Remove the headlamp loom connector from the headlamp and pull out the headlight.side light removal.

Fig. 25 Left Sidelight Screw

Fig. 26 Left Headlamp 10mm Bolts - side

Fig. 27 Left Headlamp 10mm Bolts - front

Secure Ballast to chassis - left side

The area behind the left headlamp is where the Ballast is to be placed. Rather than use self tapping screws to secure the Ballast to the chassis (using the provided metal bracket) I went for the stick on option instead, no rusty holes that way. However the metal work was covered in grime and dirt, so armed with a clean rag the metal work was cleaned. (See Figs 28 and 29). With the Ballast being placed close to the chassis I used two rubber PC feet from Maplins and stuck them on the side of the Ballast that sits closest to the headlamp (See fig. 30) as this would prevent any banging and vibration of the Ballast unit and hence reduce any possible damage done to it. I have used two layers of double sided tape, that is normally in use for number-plates, and stuck this on the bottom of the Ballast (See fig. 31). The bottom tape layer had its protective backing left in place as at this time this was not the final resting place for the Ballast. The Ballast was placed in position to figure out the loom cable routing (See figs 31 and 32)

Fig. 28 Left Side headlight bay - front	Fig. 29 Left Side headlight bay - top	Fig. 30 Rubber stick on feet
Fig. 31 Ballast with rubber feet and tape attached	Fig. 32 Ballast in temp placement - front	Fig. 33 Ballast in temp placement - top

Secure Ballast to chassis - right side

The area behind the right headlamp is, again, where the Ballast is to be placed. Before starting any work on this section, the existing loom for the headlamp had to be move slightly to accommodate the Ballast. On the outside of the chassis, where the headlamp sits, is a small loom connector (See fig. 34) that holds the loom to the chassis, pinch this together and push through to free the loom wiring (See fig. 35). This leaves the loom more maneuverable for positioning the Ballast. As can be seen (See fig. 36) the metal work was covered in grime and dirt, so armed with a clean rag the metal work was again cleaned. (See Fig 37). As done for the left side the Ballast is to be placed close to the chassis so two rubber PC feet were stuck on the side of the Ballast that sits closest to the headlamp. I again have used two layers of double sided tape, that is normally in use for number-plates, and stuck this on the bottom of the Ballast. The Ballast was placed in position to figure out the loom cable routing (See figs 38 and 39)

Fig. 34 Chassis loom connector - front	Fig. 35 Chassis loom connector (inside) - top	Fig. 36 Wiring Loom now free - top
Fig. 37 Clean metal work	Fig. 38 Ballast in temp placement - front	Fig. 39 Ballast in temp placement - top

Secure Relay Control Unit to chassis

The RCU was not to be secured to the chassis, due to the fear of rust, so a rubber foot was stuck to it (See fig. 40). This was then tucked away inside the headlamp bay, to the left of the horn, with the rubber foot facing down, again to reduce vibrational damage. (See figs 41 and 42) Once in a safe position the loom coming from the RCU was tied to the existing lighting and horn loom.

Fig. 40 RCU mounted on rubber foot

Fig. 41 RCU tied to existing loom - front

Fig. 42 RCU tied to existing loom - front (close)

Extending the loom to the right hand side

The loom needs to get to the right side of the bay as safely as possible, without getting melted or chewed up by radiator fans. On the left side of the radiator there is the radiator bracket (See fig. 43), held on by a 12mm bolt, remove this bolt. Next to this bolt is 10mm bolt that secures the coolant pipe u-bend to the chassis, remove this bolt. On the right side of the radiator is another bracket (See fig. 44) held on by a 12mm bolt, remove this bolt. With the radiator brackets and coolant pipe bracket now free, route the RCU loom cable over the top in the run between the radiator housing and the chassis. Secure the loom to the coolant pipe bracket (See fig. 45) and run further along until you get to the other end of the coolant pipe. Run the loom in between the radiator and under the coolant pipe and then carry it along in between the radiator housing and the chassis (See fig. 46). Tie the loom at this point to the top coolant pipe to stop it sagging when under along the top of the radiator (and the radiator shroud if you have one). The whole run from end to end should look like this (See fig. 47). Now with the radiator shroud back on, the cable is secured and hidden from view (See fig. 48)

Fig. 43 Left radiator bracket	Fig. 44 Right radiator bracket	Fig. 45 Loom run under left radiator bracket
Fig. 46 Loom run under right radiator bracket	Fig. 47 Loom run from left to right	Fig. 48 Radiator shroud reattached

Earth return connections

We need to now connect the earth return leads on the loom from the RCU. In the left bay area, next to the coolant expansion/overflow bottle, behind the headlamp is a 10mm bolt (See figs 49 and 50). There is an existing earth lead going back to the battery from here. Undo this bolt using a 10mm spanner as there is little room to play with (unless you remove the expansion/overflow bottle beforehand) and insert the left earth lead onto the bolt and re-tighten ensuring a good tight fit to the chassis.

In the right bay area, next to the ABS system on the chassis floor (See figs 51 and 52) there is a 12mm bolt that secures the earth return pint for the existing lighting loom. Undo this 12mm bolt and insert the left earth lead onto the bolt and re-tighten ensuring a good tight fit to the chassis.

Fig. 49 Left headlamp earth point

Fig. 50 Left headlamp earth point - close

Fig. 51 Right headlamp earth point - top

Fig. 52 Left headlamp earth point - front

Cable tidying - right side

With the right side earth connections secured, it was left just to tidy up the remaining cables so that there were no free wires hanging around waiting to be cut or snagged. On the bottom right of the image (See fig. 53) there is the loom cable, tied to the coolant hose, that runs down to the chassis where the earth line secures to the earth point. The DC supply cable (from the RCU) also runs from this point to the Ballast, where it is then plugged into the Ballast. The Ballast output cable is tied to existing light loom, to keep the Ballast in a secure location and to stop the cables getting snagged. (See fig. 171). At the end of this cable are the two ends, left free, to plug into the light. The two free connectors from left to right are:

1. Ballast input positive wire
2. Ballast input negative wire
3. Low/High beam control wire to bulb

Fig. 53 Right Secured loom cable - top

Fig. 54 Right Secured loom cable - front

Cable tidying - left side

With the left side earth connections secured, it was left just to tidy up the remaining cables as per the right side. On the bottom left of the image (See fig. 55) there is the loom cable that goes off to the right side of the car and goes directly to the RCU. Running along the lower edge of the Ballast (going from left to right) close to the chassis is the Ballast DC feed from the RCU. As it runs to the right its splits, one cable carries onto the right and connects to the earth point (See figs 49 and 50) the second cable coming up the image then backs on itself along the Ballast to go to the RCU, this is the Ballast fed with a DC supply. The Ballast output has its cable leaving the Ballast at the lower left of the image from where it is fed under the horn and comes up behind it in readiness for the headlamp to be fitted. This is easier to see in the next image (See fig. 56) There also a smaller 2 pin lead to the left of the Ballast, this is the Low/High beam control wire to bulb. The headlamp cable that fed the original bulb (See fig. 57) has a large round rubber casing, shown here tucked behind the coolant oveflow pipe and underneath the Ballast output wires. All of the cabling can sit between the horn and the battery, well out of the way.

Fig. 55 Left Secured loom cable - top

Fig. 56 Left Secured loom cable - front

Fig. 57 Left Secured loom cable - top

Live supply connection

Note: Before tackling the next part ensure that the green fuse on the live feed wire is removed.

The next lead to connect is the live feed to the battery. Admittedly this would have been far easier, if you have one, with the FMIC pipe out of the way but time was short and it was getting darker and colder, I digress, using a 10mm spanner carefully loosen the nut on the positive terminal, for those of you with black and white screens - its the red covered terminal :) You dont have to remove the nut the whole way, just enough to slide on the RCUs’ spade ended live wire. (See fig. 58) With the live feed connected, secure it to the battery clamp by running it down the centre of the clamp (See fig. 59) and then it down the battery clamp post. Secure the live feed as this places the fuse holder in a handy position to get at quickly. (See figs 60 and 61)

Fig. 58 Live feed connected to live terminal

Fig. 59 Live feed secured to battery clamp

Fig. 60 Live feed fuse - top

Fig. 61 Live feed fuse - front

Preparing the headlamps for fitting the HID Shroud

With the headlamps out, we need to remove the rubber cover (See fig. 62) With the bulb pins exposed (See figs 63 and 64) we need to unclip the spring clip holding the bulb in place. (See fig. 65) and then take out the bulb and store it securely (See fig. 66) in-case we need to roll back if there are problems with the HID system (but that wont happen :) )

Fig. 62 Headlamp with rubber cover attached	Fig. 63 Rubber cover removed	Fig. 64 H4 bulb connectors - top
Fig. 65 H4 bulb spring clips undone	Fig. 66 H4 bulb removed

Preparing the HID Bulb Shroud

Note: Ensure that when handling the lights that no oil or grease (from hands and fingers) touches the bare bulb, this will shorthen the life of the bulb.

All that should be left in the original box will be the HID bulbs in their respective holder/shroud (See fig. 67) Take out one bulb assembly and unscrew the bulb to the left, it will come away from the shroud. The bulb itself sits in a wired socket and can come work free from this socket if not held upright. Place the bulb and socket on the box upright so that nothing touches the bulb.(See figs 68 to 70) Take the bare/empty shroud and insert it into the headlamp, lock it into position and fit the spring clamp to secure it in in place. (See figs 71 and 72)

Fig. 67 Boxed HID bulbs	Fig. 68 HID bulb shroud - left	Fig. 69 HID bulb shroud - rear
Fig. 70 HID bulb shroud - top	Fig. 71 HID bulb shroud inserted into headlamp	Fig. 72 HID bulb shroud locked in place

Fitting the HID Bulb into the Shroud

Note: Ensure that when handling the lights that no oil or grease (from hands and fingers) touches the bare bulb, this will shorten the life of the bulb.

With the shroud now in place, all that is left to do is to fit the bulb. The rubber cover (See fig.73) for the lights was made to fit an H4 bulb and so has 3 slots that match the H4 pin configuration (See fig. 7) To rectify this take a small pair of snips/wire cutters/sharp knife and cut out a hole that is inline with the first raised edge on the rubber cover, this will then fit snugly to the bulb socket. Carefully pickup the bulb and wired socket and push through the hole from the back of the rubber cover to the front (See fig. 74) You will have to pull back on the rubber so that the socket is exposed (See fig. 74) as this will allow the bulb and socket to be screwed/clicked into position. You will feel a positive click when in place as it only requires around 1/4 to 1/8th of a turn to fit. (See figs 75 and 76)

Repeat this for the other headlamp - almost done…

Fig. 73 Rubber cover - precut

Fig. 74 HID bulb in rubber cover

Fig. 75 HID bulb inserted into shroud - top

Fig. 76 HID bulb inserted into shroud - rear

Refit and wire up the left headlamp

As per the instructions above (See figs 25 to 27) reattach the left headlamp, don’t forget the sidelight. There are only 2 pairs of cables remaining that need to be finally connected. The first pair are the AC output leads from the Ballast, these are the thicker wires (red and black). Connect these to the bulbs with the corresponding colours, previous images may help identify the wire ends (See figs 17 to 20) but it is fairly explanatory as to which they can and do fit. The second pair of wires (thinner red and black pair) is the Low/High control wire to the bulb.

Shown in the images, are views of the left headlamp with both wire pairs in place. (See figs 77 and 78)

Fig. 77 Left headlamp wired in - left

Fig. 78 Left headlamp wired in - top

Refit and wire up the right headlamp

As per the instructions above reattach the right headlamp, don’t forget the sidelight. There are only 2 pairs of cables remaining that need to be finally connected. The first pair are the AC output leads from the Ballast, these are the thicker wires (red and black). Connect these to the bulbs with the corresponding colours, previous images may help identify the wire ends (See figs 17 to 20) but it is fairly explanatory as to which they can and do fit. The second pair of wires (thinner red and black pair) is the Low/High control wire to the bulb.

Shown in the images, are views of the right headlamp with both wire pairs in place. (See figs 79 to 81)

Fig. 79 Right headlamp wired in - top

Fig. 80 Right headlamp wired in - left

Fig. 81 Right headlamp wired in - right

Connecting the fuse….

The last thing to do before putting the keys in the ignition (unless you forgot to remove it) is to put the green fuse back in to supply the power to the RCU. (See fig. 82)

Fig. 82 The main fuse fitted

Testing the HID Xenon Bulb Installation

Note: ensure that the High Beam is not switched in before turning on the lights

Once the keys are in the ignition, turn the key to enable the lights to be powered. Turn on the sidelights to ensure that they were correctly reattached and then turn the main beams on. You will see a very rapid flash from the headlights as the gas arcs inside the bulb. The flash will go and then be replaced with an initial low light output, but as the ionized gases start to conduct then the light warms up to full brightness. Give it another minute and then using either hold in the high beam switch or pull it to flash the lights. You will see the lights move up in direction to provide high beam light output. There will be an accompanying click heard from the lights as they switch between the low and high beams.

When the lights are powered, you will hear a high pitch buzzing coming from the lights - this is the Ballast units working (as they are DC to AC converters) if you have no lights and no Ballast buzzing, check all your cables and/or the fuse.

Post install light height/level check and adjustment

Once the lights are fitted, you can get them checked at any MOT station, but as long as they are not any higher than previously they will not need adjusting. If you electrically adjustable lights, a long as the lights are fitted when the switch is set to the highest level, if you get flashed then the lights can be lowered from inside the car.

Happy driving :)

Information Source - SIDC forum thread by vimmy, Got me some lights…