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Checking the batteries

Most car batteries are sealed for life - apart from a small vent hole which allows gas to escape. They never need topping up. Read more

Using a car battery charger

Frequent short trips, with constant stopping and starting, make your battery work very hard, especially in winter when heater, headlights, heated windows and wipers may be working most of the time. Read more

How to test a car battery

If your car's instrument panel includes an ammeter, it will tell you how well the charging system is working - the difference between the charge going into the battery and the power being used from it. Read more

Testing an alternator and checking output

Alternators have replaced dynamos as generators on modern cars; they can produce more current. Read more

How to check a relay switch

If a component that is fed with electricity through a relay (See How car electrical systems work) terminal of the battery to the feed terminal on the component, thereby bypassing the relay and supply wiring. Read more

How to test electrical circuits

If there is trouble without an obvious cause in any electrical component, test the circuit to find the cause. Read more

Checking and replacing fuses

When an electrical component stops working the fault may be in the component, in the electrical circuit or in the fuse that protects them. Because the fuse is a likely cause, and the easiest to check, look at it first. Read more

Checking headlamps and lights

It is an offence in law not to have all obligatory lights working. Check them frequently, especially before a night journey. Walk round the car while someone works the switches. Read more

Working on the wiring system

The electrical wiring in a car is a system of colour-coded wires called the loom. Where several wires run side by side they are bound together with insulating tape or plastic sleeving. Read more

Checking a starter circuit

If the starter does not turn the engine although the car battery is in good condition, the fault may be a simple mechanical one or it may be an electrical one in the starter-motor circuit. Read more

Fitting new high-tension leads

The high-tension leads from the coil to the distributor and from there to the plugs may start to deteriorate after long service, causing bad starting, misfiring and radio interference. Read more

Repairing an electric window

Electric windows are being fitted to more and more cars as standard equipment, while conversion kits are available to suit most models. Read more

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. Read more

Checking the electrics with a multimeter

Modern cars have a large amount of electrical equipment which can go wrong and so need checking. Read more

Fixing a simple light cluster

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. Read more

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