What are the most common breakdown causes?

We reveal the most common causes of car breakdowns, and investigate what the breakdown providers are doing to adapt to electric cars and others that can't be towed...

Breakdown services 2023

Most car breakdowns are caused by minor issues, and in many instances you could prevent your car from letting you down by doing some regular checks and maintenance.

Here we look at the six most common culprits and how to prevent them.

1. Flat or faulty battery 

Breakdown survey 2019

Battery failure is the number one reason for callouts. It’s more common in the winter, when low temperatures can affect the electrolyte liquid inside a battery, making it less able to hold a charge. You’re also doing more driving in dark, cold conditions at this time of year, with the lights and heater putting more strain on the battery.

In addition, cars are often not used during the Christmas break or when it snows, and that makes batteries more prone to failure, because they gradually lose charge when they’re not being used.

If your car becomes difficult to start, get the battery checked at a service centre, and run the engine for 10 minutes if you’re not going to drive it for a week or more.

2. Damaged and punctured tyres

Breakdown survey 2019

Driving over a sharp object or hitting a kerb or pothole are the most common reasons for punctures, but worn tyres and faulty valves can cause problems too, so it's important not to skimp on maintenance to save money. Checking your car’s tyres regularly could help you spot a nail or gash early and have the tyre repaired rather than having to replace it.

3. Misfuelling

Putting diesel in a petrol car or vice versa is a common error made by around 150,000 people a year in the UK. It can be expensive to sort out if the fuel gets into your car’s engine, but if you realise straightaway and get the fuel removed from the tank before the car has been started, you’ll be faced with a much smaller bill.

4. Low AdBlue

Many newer diesel cars have a selective catalyst reduction system that lowers nitrogen oxide (NOx) emissions from the exhaust by squirting AdBlue into the exhaust gases after they’ve left the engine. This fluid, also known as urea or diesel exhaust fluid, needs to be topped up regularly. If it runs out, the car won’t start. Topping up regularly is best, but you could also carry some spare fluid in your car’s boot to use in an emergency.

5. Lost keys

Many cars have keyless entry and starter buttons, and once started, some models can be driven without the key in it. That means there’s a chance you could leave the key behind and get stranded later when you turn the ignition off and the engine won’t restart.

Key fobs are complex and often have a microchip inside to protect the car from being stolen, so you’ll probably need to visit an authorised dealer to get a replacement.

Breakdown survey 2019

6. Engine cooling and air-con issues

One tell-tale sign that the alternator is on the way out is if the headlights are dimmer than usual when the engine isn’t being revved. Asking a mechanic to check on this early could prevent a breakdown.

If you try to start the car and nothing happens or you only hear a clicking noise, it could be a sign that there’s a problem with the starter motor.


Rescuing cars that can't be towed

Although many broken down cars can either be fixed at the roadside or recovered without any difficulty if they can’t be, there are added complexities for certain types of vehicles.

Generally speaking, cars with automatic gearboxes and traditional four-wheel-drive vehicles can’t be towed in a conventional way with two wheels lifted, because it could damage their gearboxes and other drive components. The same is true for the rapidly growing number of hybrids, plug-in hybrids and electric cars on our roads.

So, if you do break down in one of those and a patrol with a two-wheeled trailer turns up, you’ll have to wait for another recovery vehicle with a flatbed to be sent out. That could leave you at the roadside for up to four hours.

Roadside assistance providers are well aware of these complications, and two of the biggest players – the AA and RAC – have made some innovative changes to allow their patrols to assist owners of these vehicles.

RAC breakdown truck

Eight out of 10 RAC patrol vans are now equipped with an All-Wheels-Up flatbed-style trailer. That allows a wide variety of vehicles – including automatics, electric vehicles (EVs) and those with multiple punctures – to be safely recovered with all four wheels off the ground if they can’t be fixed at the roadside.

The compact, foldable trailers sit in the back of the van when not in use and can be deployed quickly when needed. The system is particularly useful for roads where it can be challenging for a traditional flatbed lorry to gain access, such as red routes in city centres, narrow country lanes and car parks.

The AA has come up with a different solution called the ‘freewheeling hub’. One of these can be attached to each rear wheel hub on a stricken vehicle, enabling the fitting of a pair of universal spare wheels (in place of the original wheels) that roll independently from the car so no damage is done to the car’s gearbox or other components.

AA freewheeling hub

Another issue that’s becoming more common is EVs running out of charge. To address this, some roadside assistance providers have introduced mobile chargers that can provide emergency top-ups on the spot – enough to allow a stranded driver to get to a nearby public rapid charger for a more substantial boost.

LV= Britannia Rescue, for example, has partnered with another vehicle assistance company, AFF, to provide its members with a roadside charging service. AFF’s fleet of vans covers the UK and can provide a range boost of up to 15 miles in around 30 minutes, at a rate of 7.2kW.

The RAC, meanwhile, is equipping around a fifth of its vans with 5kW EV Boost units that can add around 10 miles of range in half an hour. It’s also developing a 7.5kW charger and investigating other mobile charging solutions.

AA research found that EV owners with flat main batteries preferred to have their cars recovered to a charging point where they could fully replenish the battery, rather than getting a short boost from a patrol van. Its patrols use the freewheeling hubs and universal spare wheels to transport EVs to the nearest public chargers.

Another issue is that EVs’ high-voltage electrical systems can be dangerous for untrained technicians to work on. To ensure that its patrols have the appropriate knowledge to tackle issues on hybrids and EVs, the AA has invested in a high-voltage training rig. It can be used to simulate a range of electrical faults to let technicians practise fixing them in the classroom rather than at the roadside.

The rig is modelled on a third-generation Toyota Prius and can be programmed to replicate faults with the fuel, cooling, exhaust, ignition and CVT automatic gearbox, plus some diagnostic functions.

The RAC also provides EV training for all its patrols, and each year it rolls out a new bespoke training package that takes the best industry knowledge and insight and makes it directly relevant to what its staff need to be able to do at the roadside.

It has also started to electrify some of its recovery fleet. This year it started trials with Renault Zoe E-Tech and the Maxus eDeliver 3 vans. None of its electric vans is capable of towing a broken down vehicle yet, though.


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