Why does my car alarm keep going off?

Does your car alarm seem to have a mind of its own? A car alarm going off randomly or at night can be a major disturbance, but we're here to help.

There are a number of issues that can cause a car alarm to keep going off. Dodgy sensors, faulty key fobs, and bad installation can all make your car alarm play up.

We'll discuss what you can do to get your peace and quiet back:

Common reasons your car alarm keeps going off

A blaring car alarm that goes off at random can disturb the peace of you and your neighbours. But often there's a simple reason why your alarm keeps going off:

Key Fob Malfunction

A low battery or malfunctioning key fob can cause your car alarm to go off randomly. It might be faulty due to wear and tear, or it could be due to manufacturing errors.

The battery might be out of charge or dead, so you might need to find a replacement. You can usually find the type of battery you need in your owner's manual.

Signal interference is another reason for a car alarm going off randomly. The key fob's programming could be damaged or reset, making it lose synchronisation with your car's security system.

Dirty or Misaligned Sensors

Cars have many sensors, including door lock, glass break, proximity, tilt, shock, and microphone sensors. A dirty or misaligned sensor can set your car alarm off seemingly at random.

Low or Failing Car Battery

Sometimes it's not the key fob battery but your car battery.

If your battery is weak or dead it can cause the alarms to sound. To check that your battery is working correctly, use a voltmeter to check the voltage. A voltmeter is a tool that tells you the voltage between two points in an electrical circuit. They're highly accurate, and are simple and safe to use.

If the battery isn't working properly, you might need a new one. At this stage it's worth calling a mechanic to help.

Poor Alarm Installation

If your car alarms aren't installed quite right, it can play havoc on your car's security system. Loose connections or faulty wiring can make the alarm play up and malfunction.

Environmental Triggers

Sometimes a random car alarm isn't as random as you might think. Your alarm may be activated by certain environmental triggers. Weather conditions like wind and rain can trigger the alarm, as well as passing cars.

You might also find that nocturnal animals are the cause of your car alarm going off at night. Cats and woodland critters might be using your car as their resting place. Small animals have been known to clamber into engine compartments to nest.

Keeping your engine clean and clear of debris can deter animals from climbing inside. It's also worth sealing any gaps or openings using steel wool or metal mesh.

How to stop your car alarm from going off

Resetting Your Car Alarm System

If you think there's a problem with the overall alarm system, it might be time to reset it.

If your car has a built-in remote, you may be able to turn the alarm off by unlocking the driver's side door with the key instead of the remote. This can help reset the alarm settings if there's a fault with the system.

Checking and Replacing the Key Fob Battery

If it's the key fob that's the problem, you may want to replace the battery. Most key fobs use a lithium battery which is flat and round. The battery code should be printed on the battery itself for you to see.

To check the battery you can open the key fob with a small screwdriver or your fingernail. Once you've done this you can remove the old battery and insert a new one. Make sure the battery is the right way up, then seal it closed.

You can then test to see if the key fob is working. If it's still acting up, there might be a different issue. For example, the key fob could be deprogrammed, or the battery contacts could be broken. You might need to take your car to a mechanic so they can work out what's gone wrong. 

Cleaning Sensors or Bonnet Latch Mechanisms

Dirty sensors can be the cause of a car alarm that's randomly going off.

In modern vehicles, the bonnet latch has a sensor that sets off the alarm if someone tries to force the bonnet open. A build up of grime, dirt, and engine grease can stop the alarm working properly and trigger it at random.

Disconnecting the Alarm (Temporary Fix)

Disconnecting the alarm is a temporary fix to the problem, but once you've done this you may want to investigate further.

Some cars also have an 'off' button on the dashboard. This allows you to deactivate the alarm system. If you're unsure how to turn your system off, it's worth checking the owner's manual for specific instructions.

If your alarm is still going off and you can't seem to deactivate it, you may need to disconnect the battery. Be aware that this may wipe your car's onboard computer and/or infotainment system.

Consulting a Mechanic for Persistent Issues

If none of these things seem to be the culprit for your alarm, you may need to contact a mechanic.

There might be a more serious problem with your car that needs to be addressed.

How to turn off a car alarm

The first thing you'll want to do when faced with an annoying car alarm is turn it off. Here are some ways to stop it:

1. Use the key fob. You can press the 'unlock' button on the key fob.
2. Use the key. You can insert your key into the ignition and turn it to the 'on' or 'start' position.
3. Use the dashboard. Some cars have an 'off' button on the dashboard which you can press to stop the alarm.
4. Check the owner's manual. If in doubt, check the owner's manual for instructions. It's a good idea to familiarise yourself with the manual, so you know how to quickly turn off the alarm.
5. Disconnect the battery. Once again, if all else fails you may have to disconnect the battery. This can wipe your car's computer, so only do this if the other options haven't worked. To disconnect the battery you can remove the negative (black) battery connector.

What should I do if my car alarm keeps going off?

If you're still having no luck, the place you've parked might be an issue. If it's the environment that keeps setting your car alarm off, you may need to try parking elsewhere. You can also try to adjust the car alarm sensitivity.

Be mindful of where you decide to park your car if you move it. Make sure you're obeying parking rules and aren't putting your vehicle at risk. It's worth noting that you may need to tell your insurer about any change of overnight parking. 

Other ways to improve car's security

We all worry about keeping our cars safe and secure. Our car theft calculator can help you work out the theft risk for your vehicle. Even if your area has a low likelihood of theft, it's worth making sure you have good car security.

Here are some ways you can improve your car's security:

• Parking. Where you choose to leave your car can make a big difference. Parking in well-lit, secure areas can deter thieves from trying to get into your car. Try to avoid parking in places that are hidden from public view, as this can make a car theft easier. Instead try to find private car parks with CCTV.
• Locking doors and closing windows. Leaving your car unlocked is never worth it, even if you're just quickly popping into a shop. You should also make sure your windows are shut, so that thieves can't reach in.
• Keep valuables hidden. If you've got valuables in your car, keep them out of sight or remove them completely. You can store valuables in your glove box or in the boot. This way they aren't on show for thieves looking to snatch them.
• Keep your keys safe. Keeping your keys safe and out of sight reduces the risk of them being stolen. Make sure to keep them safely on your person, and never leave them unattended in public.
• Install a data port. Thieves can use the OBD port to override the vehicle's immobiliser and steal the car. You can install a lockable data port cover to keep out unwanted access. A strong metal cap stops access to the OBD port, and can only be opened with a code. 
• Put your reg on the windows. You can get your car's registration number etched onto the windows for added security. This can deter thieves as it makes your car easier to identify if it's stolen. 

What is a Thatcham-approved car alarm?

A Thatcham-approved car alarm is an alarm that's been independently approved and assessed by Thatcham Research. Thatcham Research is a company that specialises in categorising  the effectiveness of aftermarket vehicle security.

They rigorously test products against a certain criteria to verify they're fit for function. As an industry benchmark, this certification is a sign of reliability for a vehicle's security. Certified devices are given a Thatcham Security Certification, known as a Thatcham Category rating.

The higher the rating, the more your car insurance premium may reduce. This is because your car is deemed a lower risk if fitted with a highly rated security device. 

What should I do if a neighbour’s car alarm keeps going off?

It can be frustrating if your neighbour's car alarm keeps going off, especially if it's waking you up at night. Depending on the situation, here are a few things you can do:

• Rather than lose your cool, try talking to your neighbour first to let them know about the disturbance. They might not be aware that the alarm is going off in the first place.
• Check for any suspicious activity. If you see anything out of the ordinary or suspicious going on, you should report it to the authorities. If you see someone trying to break into the car, you should call the police immediately.
• If the alarm keeps going off, you can contact your local authorities for help. The Environmental Health department at your local council can also help with nuisance car alarms. 

Brand-specific car alarm advice

When choosing an alarm for your car, you might want to consider a few things:

Compatibility: Make sure the alarm you choose is compatible with your car's make and model. 

Security Features: It's worth considering the level of security you might need for your car.

Some car brands have specific security installed. Here are some popular models with security systems built in:

• The Nissan Qashqai has a Nissan Anti-Theft System (NATS) and Super Lock system. The Super Lock system stops the car doors from being opened from the inside of the vehicle, deterring thefts and break-ins. The Super Lock is activated with an Intelligent Key or a request button.
• BMW has a multi-layered approach to security. They use both hardware and software systems to deter theft, including a key transponder. Each BMW key has a unique transponder chip that sends a signal to the car's ignition system. The car only starts if the code matches the one stored in the electrical control unit. This communication is encrypted, making it very difficult for thieves to hack in.
• Kia Sportage has an alarm system which activates when the vehicle is locked and thieves try to get into the door, trunk, or hood.

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