The key to avoiding a breakdown is good and regular maintenance together with an understanding of what's most likely to go wrong.

The number of models and complexity of modern cars mean that AA patrols are called on to deal with thousands of different faults. These are the most common though and have been for many years. 

Many can be fixed at the roadside, but most can be avoided with the correct preventative care.

Flat or faulty battery

Most common problems are caused by terminals and clamp connections or by a loss of voltage, often caused by constant use on short journeys without regular recharging.

At every service, check that terminals have been cleaned and protected from corrosion with a layer of petroleum jelly or grease. Clamps and connections must be secure.

If you seldom make a long journey, a fortnightly overnight charge prolongs battery life.

Modern maintenance-free batteries need no top-up.

Lost keys

Most modern cars have a 'transponder'key combining a conventional mechanical key with an encrypted electronic chip to prevent theft.

If you lose the key, recovery to an authorised dealer may be the only answer.

Even a dealer may take several days to obtain a replacement, so always carry a spare set of keys.


Flat/damaged tyres and wheels

Check the handbook and adjust pressures as required to suit different speeds and loads.

Kerb impact can damage sidewalls and, possibly wheel rims. Both can result in slow leaks. Consult a specialist tyre dealer if any damage is visible.

When checking tread depth, look for uneven tyre wear – the wheels may be misaligned.

Look at the spare tyre. A worn or flat spare won't be of use in an emergency.

Check that the jack and wheel-removal tools are in good condition and that the key or removal tool for locking wheel nuts is accessible.

Alternator faults

Persistent battery problems and dim headlights when the engine is idling can indicate alternator/generator faults.

Belts driving the alternator may also operate the radiator fan and water pump. A red ignition warning light plus a rapid rise in engine temperature could indicate a broken belt. Stop straight away.

Starter motor

Though usually robust, starter motors can fail.

Good, regular garage maintenance should highlight potential faults.

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Empty fuel tanks cost a lot of time and inconvenience. Fill up at the start of your journey and well before the low-fuel warning light comes on.

Every year more than 150,000 motorists put the wrong fuel in their car – petrol in diesel is most common but determined drivers put diesel in petrol cars too.


Clutch cables

Clutch cables are under high stress, and abrasion can weaken the wire strands until they break.

AA patrols can often make temporary repairs at the roadside, but replacement at the first signs of wear is the best answer.

Spark plugs

The spark plug is a much-neglected part of the ignition system.

Make sure that you replace plugs at the manufacturer's recommended service intervals.


HT leads

High-tension (HT) leads and their connections can deteriorate with age. Water and dirt enter cracks in the insulation, reducing ignition voltage.

Damp-repellent sprays like WD-40 are only a temporary solution.

Ask your garage to check the condition of the leads and replace as necessary.