It is essential to keep your car lights in good working order all the time.
Apart from being dangerous, a defective light may also be illegal. If you do
find a defective light unit, and you know the bulb is not at fault, the problem
may lie in the light unit itself.
On most modern cars the light units are combined into clusters, but on older
cars they are often fitted singly or in pairs and have the advantage of being
cheaper to replace. This sheet looks at these simple units. Clusters are
covered in Bodywork S9 and 60.
Removing a simple light unit
The lenses are most commonly held from the outside. by small screws and can
be removed with a suitable size screwdriver. Other types are secured from the
rear and you may have to remove trim panels on the inside to gain access to
them. Once you can see the rear of the light unit look carefully to find how
the lens is fixed. You may have to remove the bulbholder first (see below)
before you can remove the lens fixings.
Release the lens fastenings and lift the lens away. Check the condition of
the lens. If it is cracked you will need to buy a new one from your dealer.
Some lenses are made up of individual sections which are slotted together. With
this type you can often replace just the broken section.
Clean away any dirt, grime and condensation that has accumulated on the
inside of the lens.
As with the lenses the bulbholders can be removed either from the front of
the light unit or from the rear.
Disconnect any wiring to the bulb-holders by pulling off the multi-plug
connector. If individual wires are
ted, make a note of which wires fit to
to help with reassembly.
Check to see how the holders are fitted to your car. They may be held with
small screws or clips, or they may screw out completely with the bulb still in
place. Some small indicator repeater bulbholders are removed complete with
their wiring and have to be disconnected away from the light unit.
When the bulbholder has been removed check for any corrosion on the wiring
terminals or inside the bulbholder. The bulb is often earthed through the
holder securing screw so make sure this is free of corrosion, both on the
holder and where it attaches to the body.
Clean any corrosion with wet-ordry paper and spray some
it to prevent further deterioration. If the bulbholder is badly rusted, you
should replace it with a new one.
Some bulbholders use a small spring to push the feed wire into contact with
the base of the bulb. Remove the bulb and check the contact inside the holder
for corrosion. Clean it up if necessary.
With this type of holder a loose fitting bulb could be due to a weak spring.
Pull the wire and contact right out of the holder to reveal the small spring
behind it. Stretch the spring with two long-nosed pliers to retension it. If
the bulbholders have a separate earth wire check that its connections are clean
If your lights seemed to be dull the cause could be a tarnished reflector
around the bulb.
The reflector may be
with the bulbholder or mounted separately on
the light unit baseplate. To remove the baseplate release the securing screws
or nuts and lift it away - remember that it may be attached to an earth wire
which you will have to remove.
Carefully scrape away any corrosion on the reflector with a screwdriver,
then gently polish up the surface with metal polish.
A broken lens
can cause water to enter the light unit, leading to
corrosion and condensation. Inspect the lens gasket to make sure it is intact.
If broken or perishing it should be replaced.
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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
If your car's instrument panel includes an
, it will tell you how well the charging system is working - the difference between the
going into the
and the power being used from it.