It's a nightmare when your car won't start in cold weather. And with frosty mornings and freezing nights, it's more likely to happen over winter.
Find out why cars break down in the cold and what you can do to keep your wheels on the road.
Top 5 reasons why cars won't start in winter
We looked at the most common breakdowns our patrols were called out to between the months of December and February. These are the top reasons for calling us:
- Battery-related (24%)
- Tyres (16%)
- Intake and emissions (8%)
- Starter and alternator faults (6%)
- Locks and alarms (5%)
Winter car problems range from issues with the fuel intake, like faulty pumps and fuel injectors, to electrical problems with locking systems. Thankfully, our breakdown cover can get you moving again.
Call us for help if you get stuck
Car battery problems in the winter
The top reason for cars breaking down in cold weather is battery problems. That's because cold weather affects the chemical process inside your car battery, making it harder for the battery to hold a charge.
You'll probably have noticed that other battery devices like mobile phones and digital cameras lose charge quicker when it's cold too. When it comes to your car battery, there are a few key signs to look out for. If you’ve got any of these symptoms, your battery may be about to die.
- Struggling to start the car
- If you hear your engine cranking more slowly than usual, or a clicking sound when you try to start your car – these are signs that your battery is failing. To get going, you may even need a jump start, but don’t be under any illusion that this is anything other than a temporary solution. You’ll likely need to get your battery and electrical systems tested ASAP.
How to prevent flat batteries in cold weather
There are a few things you can do to reduce the likelihood that your battery will give in at some point:
1. Drive more
If you only use your car for short trips or on rare occasions, it’s much more likely to put strain on your battery. When the engine and alternator are running, this is when they’ll get a chance to recharge the battery to its previous state. If possible, drive over longer distances or look into getting an external battery charger.
2. Switch off any extra electricals
Devices and features in your car are powered by the car battery. This includes things like internal lights and anything you might plug into the USB socket – so make sure to disconnect and power any other features down when you leave your car.
3. Perform a visual check of the battery
Sometimes, when you lift up the bonnet, you maybe able to spot signs that your battery has a problem, like corrosion. A mechanic can also perform this test for you if you want to be on the safe side. It could even be that your car has the incorrect type of battery fitted if you’re experiencing issues.
Tyre problems in the winter
In cold weather, tyres are much more likely to lose pressure. Low-pressure warning lights are a much more common occurrence in the winter months. If left unchecked, you’ll slowly notice that your tyres cause performance issues, such as reduced traction, responsiveness in steering, and increased braking distances.
How to prevent tyre damage in cold weather
Make sure to check your tyres often for any damage/punctures that you can see visually, and to increase tyre pressure if needed during cold weather (or if your tyre pressure warning light comes on). Checking your tyre pressures is a good habit to get into. Correctly adjusted tyre pressures can improve handling by making your steering more responsive.
If you know that your tyres are really old, you may want to go ahead and have them replaced, just for peace of mind.
Problems with fuel intake and emissions in the winter
You might have noticed that your vehicle doesn’t manage as much range when it comes to fuel economy in the colder weather. This is because engines need a higher base amount of fuel just to ignite the engine and get all the internal parts of the vehicle back to a normal operating temperature.
Engines take a longer time to heat up in the cold which means they’re using more fuel than usual, and when you stop using your car, the engine’s temperature drops faster than usual too. This creates a cycle where your car is never really getting to a warm enough temperature consistently and staying there for long enough, especially if you only tend to make short trips.
The fuel injectors in your vehicle can even become blocked by ice particles, which can lead to fuel system problems such as a stuttering engine or even complete power cut-outs.
How to prevent intake and emissions damage in cold weather
You can try to take longer trips in your vehicle so that the engine can get up to its preferred temperature for long enough.
Starter motor and alternator problems in the winter
If your car won’t start in cold weather, it could be due to the starter motor. As we’ve mentioned above, the viscosity of any fluids in your car are likely to change as the temperature drops. One of the possible results of this is that it takes more effort to make the starter motor spin.
Signs that your starter motor has a problem include a clicking sounds when you use the ignition key. You can rule out a battery problem by checking whether all the other electricals in your car are working. A jump start won’t work if the starter motor is finished.
How to prevent cold weather damage to your starter motor and alternator
One of the best ways to keep your starter motor in good shape is to keep your battery in fine condition. When a battery gets weak this can put extra pressure on the starter motor, shortening its overall lifespan. Be sure to follow our advice above to keep your battery healthy.
You should also avoid cranking the engine in cold weather – if you do this for too long, it can result in overheating damage to your starter motor.
Problems with car locks and alarms in cold weather
Unfortunately, any locks on your car (doors/boot/fuel filler cap) can become frozen over during cold weather. Some suggest that you can apply Vaseline to your key to keep the lock well-lubricated, reducing the chances of it freezing over. If possible, also try to keep your car in a warm place, like a garage, when you’re not using it.
Why do cars break down more over winter?
Cars won't start in cold weather for 2 main reasons, both of which are related to battery problems:
- Batteries are more likely to lose charge and go flat in cold weather.
- Cars might be sat on driveways without being driven for periods over the holidays.
Batteries charge while the car is being driven. So if you don't drive for a few days over the festive period, the battery can lose its charge. It's also more likely to happen when the weather's cold.
There are other problems which can pop up when the weather's chilly too. If you don't get your antifreeze levels right, you could have a problem with frozen screen wash or engine coolant. Plus your car might not start in cold weather if you haven't used the right viscosity of engine oil.
Find out more:
With Battery Assist, we replace your battery the same day.
Are there more breakdowns over Christmas?
We often see a spike in breakdowns over the festive period. The worst day for breakdowns is always the first working day of the New Year. People try to use their car to go to work, often for the first time in a week or more after celebrating Christmas, and find it won't start.
The first working day of the New Year is traditionally a busy day for breakdowns.
How to avoid a winter breakdown
Give your car a little TLC and it should start for you each morning, no matter how frosty it gets.
The most important thing is to keep an eye on your battery. Take your car out for regular runs (of half an hour or so) to keep the battery charged. Batteries only last about 5 years, so if yours is nearing the end of its life, invest in a new one before winter.
Here are 10 things you can do to keep your car tip top in cold weather:
1. Check your coolant level
Check your coolant level regularly and have your antifreeze concentration checked by a garage, before the cold weather sets in.
2. Use a screen wash additive
Use an additive in your screen wash all year round, but make it undiluted in winter. It'll stop your washer jets from freezing up. If you keep running the pump without any fluid coming out, you could blow a fuse that controls something more important.
3. Check your wipers are off
Make sure the windscreen wipers aren't stuck to the glass before setting off. And don’t leave them on ‘automatic’ in cold weather. They could be frozen stuck and try to start going when you turn on the engine. It could damage your wipers or you could blow a fuse, causing other problems.
4. Clear snow off ASAP
Clear snow from your vehicle as soon as you can. Leaving it for a few days will make it a lot more difficult to shift. Find out the best way to clear your car of snow and ice here.
5. Defrost locks and handles
If you get frozen door locks or handles, a squirt of WD-40 will help. And a light smear of Vaseline or silicone furniture polish on the door seals will stop them sticking too.
6. Don’t leave wet clothes in your car
The water in the air can make condensation inside the vehicle worse, causing misted up windows.
7. Wait to open windows
Don’t open your windows as soon as you set off. They may be frozen in the frames and could become detached from the mechanism. Wait until the car's warmed up so any ice has had time to melt.
8. Keep your car clean
It's good to clean your vehicle regularly in winter to remove corrosive road salt. But don’t blast water inside the brake drums or cables. If the temperature drops, you could end up with frozen rear drum brakes and handbrake cables, and you won’t be able to get moving.
9. Move off carefully
If you have an automatic parking brake, there’s a chance it won't release. With your foot firmly on the foot brake, release the electronic parking brake and ease your foot off the pedal, driving off slowly.
10. Listen to your engine
If you hear a ‘screaming’ noise when you start the vehicle, along with smoke and a burning smell, stop immediately. Either the water pump or alternator may have frozen and driving on will cause further, more serious damage.
How do I start my engine when it's cold?
There are a few things you can do to make it easier to start your car in the cold. Firstly, make sure to de-ice your car properly before starting up the engine. This will reduce the amount of time you’ll spend idling ad demisting windows.
Before starting, make sure all the doors are shut and any electrical devices are switched off. Then:
- Turn the key in the ignition and hold it there for 10 seconds
- If this doesn’t work, let your battery recovery for 1 or 2 minutes, then try again
- Consider a jump start if the above doesn’t work
Why won't my car start in the cold but it cranks?
If your car won’t start in the cold but it makes a cranking sound, it could be any of the following issues:
- A flooded engine
- Empty fuel tank
- Blocked fuel filter
- Faulty fuel pump
- The battery has failed
- The engine is frozen over, meaning the starter motor has reduced cranking power
Why is my car struggling to start but the battery is good?
If your car won’t start, or takes a long time to start, but the battery seems to be fine (or is a new battery) then this could be due to a bad alternator. In cold or damp weather, the alternator is more likely to wear out or fail entirely.
Advice from our patrol of the year for keeping your car in tip-top shape this winter
Nick Powell, AA patrol of the year, says: “When driving in winter conditions, reduce your speed to account for the conditions and leave plenty of space behind other vehicles and try to use main roads where possible as these are more likely to have been gritted. Allow extra time, as it’s likely your journey will take longer than usual, and ensure you have plenty of fuel or electrical charge if driving an electric vehicle (EV).
“Before setting off, check the condition of your tyres (including the spare). If frosty, it’s important to fully de-ice the car which includes clearing snow or ice from the windows, lights and roof so you can see and be seen.
“It’s also worth having winter essentials in the car such as warm, waterproof layers, a shovel, a torch, and a flask of hot drink. Ensure your mobile phone is fully charged and download the AA app and what3words to help us get to you faster if the worst should happen.”
We provide 24/7 roadside assistance.
Published: 22 November 2016 | Updated: 09 November 2023 | Author: The AA