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Top 10 reasons for car breakdowns

Common car faults and how to avoid them

Car breakdown

Make sure you have car breakdown cover in case you’re left stranded at the roadside

The AA provides breakdown cover to more Which? readers than any other company, so we asked it for the top 10 reasons its patrols are called out.

Cars don’t break down as often as they used to, but when they do it can be a major inconvenience. However, many breakdowns are caused by quite simple faults that can be avoided.

More than a third of calls to the AA are because of flat or faulty batteries, lost keys, a damaged wheel or flat tyre. Indeed, batteries, starting problems and tyres have been the top three reasons for calling out the AA since its formation in 1905.

Find out our Recommended Providers for breakdown cover.

Top ten car breakdown faults

1. Flat/faulty battery – 20%

Regular short trips are a big drain on the battery. Avoid this by giving the car an extended run every couple of weeks.

2. Lost keys – 10%

For security, a main dealer is often the only source of keys. On holiday, make sure two people have keys and keep them in separate places.

Car breakdown

Move your car as far off the road as possible and get to a position of safety

3. Flat tyre/damaged wheel – 5%

Make regular pressure and condition checks to reduce the risk of unexpected failure. 

Read our guide to changing a wheel.

4. Distributor cap – 3% or less

Damp conditions will affect this part if it is cracked or damaged. This could cause a high voltage short-circuit, preventing the spark from reaching the spark plug.

5. Alternator faults – 3% or less

Can be a faulty alternator, a bad connection or a worn drive belt.

6. Fuel problems – 3% or less

Always check which petrol pump you’re using – filling up with the wrong fuel is common The AA has ‘Fuel Assist’ vehicles, equipped to drain the tank, clean the system and re-fuel your car. If you do accidentally put the wrong fuel in and you notice in time, don’t start the engine. This can cause major engine damage, changing the remedy from a simple fuel-system flush to an expensive engine repair.

Car breakdown

Most cars can be repaired at the roadside, but sometimes a tow truck will be necessary

7. Clutch cables – 3% or less

A clutch cable operates every time you change gear. But eventually it will fail, often without warning.

8. Spark plugs – 3% or less

Malfunction here can cause a misfire or failure to start. Have spark plugs changed in line with the manufacturer’s instructions.

9. HT leads – 3% or less

These deliver high voltage current to the spark plugs. They deteriorate due to temperature cycling and can fail without warning.

10. Starter motor – 3% or less

This can leave you stranded at home. Many breakdown policies only apply if your car is more than a quarter of a mile away from your house, so opt for home cover to minimise delays.

Are cars getting too complicated to repair at the roadside? Join the Which? Conversation and have your say.

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