Overhauling a light cluster

Many modern cars are now designed so that their lights are built as a one-piece unit known as a cluster. These are easier for the manufacturer to produce than the older type of light unit, which is fitted separately to the car.

However, removing, dismantling and repairing these units is sometimes more difficult, and very often more expensive, than on the older type of light unit.

Possible problems

The most obvious reason for removing the light clusters is if they have been damaged after an accident. Light clusters are almost exclusively used for the rear lights and are in a vulnerable position in the event of an accident.

You may also need to remove the light cluster if condensation or water has built up on the inside of the lens. This can be caused by water seeping past the sealing weatherstrip or gasket. Alternatively, the small holes built into the units to allow water to drain out may have become blocked, trapping water inside.

If the light unit is left in this condition the water can soon develop into a green slime which can cut down the brilliance of the light unit. The water may also come into contact with the electrical connections in the light unit. This will cause corrosion and eventually the electrical contact will be lost and the light will go out.

Before starting work on the cluster unit find out which type you have fitted, because this determines how you go about removing the light cluster from the car.

Replacement parts

New replacement lenses are often very expensive so it is worth checking a local scrapyard for an old one. Remember, however, to buy the correct lens because some may only fit on the left- or right-hand side of the car.

If you find that just the bulbholder is at fault this can often be bought separately if it is the detachable type.

Removing an old type cluster

Old and new types of cluster unit

The older type of cluster unit (right) often has its lens secured by external screws and can be removed separately.

These units are often wired so each individual bulbholder has its own connector, and you may be able to remove the bulbholders from the unit without disconnecting the wiring.

The later type of cluster units (left) are a little more complicated to remove. The lens cover can often be removed only from the back of the unit which may require that the entire cluster be removed from the car.

In some cases the lens is integral with the cluster casing, and if it breaks you will have to fit an entire new unit.

Removing a new-style cluster

Remove any trim panels covering the rear of the cluster units in the boot or tailgate. Disconnect the battery and then the multi-plug from the light unit.

Find and remove the fixing screws, bolts or nuts from the cluster unit (3), noting if they are different lengths. Then carefully pull the unit out of its aperture in the car body.

Simpler types

The most simple type of cluster has the lens cover held to the cluster casing by small screws which pass through the lens. To remove the lens you simply unscrew the fastenings. However it is worth taking a few precautions first.

The securing screws are invariably of the cross-headed type but they may be either Pozidriv or Phillips. So make sure that you use the correct type and size of screwdriver to remove them. They may have become corroded due to their exposed location and if you use an incorrect screwdriver it is easy to strip or even break off the screw.

If you find the screws are really tight, soak them with penetrating oil, allowing time for it to work in before trying the screws again. Once the screws have been removed the lens can be lifted away.

Now look for securing screws around the cluster casing. If you see them, you can remove the cluster simply by undoing them. But first disconnect the battery terminals and the wiring to the bulbholders. Then release the securing screws and the unit should now lift out with the bulbs and their holders in place.

If you cannot see any fixings, or if you cannot at this stage disconnect the wiring, then you will have to dismantle the unit further before you can remove it. The procedure for doing this is the same as for the more complex type of light cluster.

Cleaning lenses

If you have removed your lens because it was dirty, or if you need to clean up a second-hand replacement item, you can do this with soapy water and an old soft toothbrush.

Gently scrub out all dirt and grime from the lens. The silver backing around the bulbs can also be carefully cleaned in the same way. But take care not to scrub this too hard or you may find the silvering will start to lift off.

Before reassembly make sure the inside of the lens and bulbholders is absolutely dry.

Complex types

The more complex type of cluster unit has its lens cover attached to the casing from the rear. There are no exposed screw heads on this type and the entire cluster unit will need to be removed from the car before the lens can be removed or the cluster checked.

Open the tailgate or boot lid so you can see where the rear of the cluster sticks out. The cluster will often be covered by a trim panel. Remove this first to gain access to the rear of the unit. The covers are often held by one or more simple wing nuts or turn buttons and can usually be removed by hand. The section in your car handbook on changing the bulbs should tell you how to remove them.

Wiring connections

Start by disconnecting the battery earth terminal as a safety precaution. Look at how the wiring is attached to the cluster unit.

Older style units have individual Wires running to each bulbholder. You may be able to pull out the bulbholders without having to disconnect the wiring. If this is not possible label the wires as you disconnect them so they don't become muddled on reassembly.

Later units use multi-plug connectors. These may be a tight push-fit and simply pull off. Others engage positively on to the cluster casing and you have to press in the small thumb tabs on each end of the connector to release them.

If the rear of the unit is not accessible, the wiring can only be disconnected once you have unbolted and partially removed the unit from the car.

Fixings

Find where the main cluster fixings are located. Vertical units usually have a fixing at the top and bottom while horizontal ones have them at each end and may also have one located at the top and bottom. The fixing may be a bolt or screw which threads into the cluster unit or it may be small nuts which tighten on to studs fixed into the cluster casing.

Remove the fixings and carefully withdraw the cluster from the car. You may have to twist it to get it to come out of its aperture. Take care not to damage the seal between the cluster unit and the body as you withdraw the unit. Disconnect the wiring at this stage if you couldn't do so before.

With the cluster now removed look at the back of the unit to find the fixings that secure the lens. Undo them, noting if they are of differing lengths, and if so note where they fit. The lens can now be separated from the cluster unit.

Sealing gaskets

Take care when lifting the lens cover away from the cluster unit. It may not have been moved for some time (possibly never before) and may be tight on its mounting.

Gently tap it with your hand to break any bond that may have formed between the lens and sealing gasket. Then lift the lens up gently, making sure that you do not tear the gasket behind as you do so.

If you find the gasket has become torn or perished you will have to buy a replacement for reassembly. New gaskets should be available from your dealer but if you can't find one you can use a sealing mastic carefully applied in its place (see sideline overleaf).

Reassembly

The light units are reassembled in basically reverse order to dismantling. Remember not to overtighten the lens or cluster securing fixings as they usually screw into plastic, which easily cracks.

The multi-plug connectors often have a slot formed in one end so they can only be fitted one way round. Reconnect the battery only after all wiring connections have been made. Finally turn on the ignition and check that all the lights are working. Ask a friend to operate the switches while you check.