Why is my burglar alarm showing a fault?

The most common reason is a low or dead backup battery. Alarm batteries typically last 3-5 years and the system will flag a fault when the battery drops below a usable level.

Can I replace the alarm battery myself?

On some systems you can, but many panels require an engineer code to clear the fault after replacement. If your system is monitored, your monitoring company may need to be informed.

How often should alarm batteries be replaced?

Backup batteries should be replaced every 3-5 years as preventive maintenance. Sensor batteries in wireless systems typically last 2-3 years.

Should I upgrade my old alarm system?

If your alarm is over 10 years old, modern systems offer better features including smartphone notifications, wireless sensors, and smart home integration. An upgrade may be more cost-effective than repairing an obsolete system.

Low risk

Updated 30 August 2026

Burglar Alarm Not Working

Your burglar alarm will not set, is showing a fault, or is completely unresponsive.

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What's happening?

A burglar alarm that is not working may fail to arm, display a fault code on the panel, or have a completely dead keypad. Intruder alarm systems in the UK range from simple bell-only systems to fully monitored installations. When they stop working, your property is left unprotected.

What usually causes it?

Backup battery dead or failing: the most common cause of alarm faults
Sensor fault preventing the system from arming
Keypad or control panel fault
Mains power supply to the alarm panel interrupted
Wiring fault between the panel and a sensor or sounder
Zone tamper fault caused by a loose sensor cover

Is it dangerous?

A non-working burglar alarm is not an electrical safety risk. However, it does leave your property without security. If the alarm stopped working after a power cut or surge, there may also be damage to the backup battery.

Can I fix it myself?

Check the keypad for error messages or fault codes and consult the manual. Check the mains supply to the alarm panel: it is usually connected via a fused spur near the panel. If the display shows a battery fault, the backup battery needs replacing. Walk around and check all sensors are firmly closed and not hanging off the wall.

When should you call an electrician?

Call an electrician or alarm specialist if the panel shows a fault you cannot clear, if the alarm will not arm despite all sensors looking correct, if the panel is completely dead, or if you need the backup battery replaced (some systems require an engineer to reset after battery replacement).