Why has my security light stopped detecting movement?

The most common cause is a dirty or cobweb-covered PIR sensor. Clean the lens first. If that does not fix it, the sensor itself may have failed and the unit will need replacing.

How long do PIR security lights last?

LED PIR security lights typically last 5–10 years. Older halogen floodlights fail more frequently, mainly due to bulb burnout. The PIR sensor itself can degrade over time.

Can I replace a security light myself?

If it is a direct like-for-like replacement on an existing connection, a competent DIYer can do it safely after isolating the circuit. If new wiring is needed or you are not confident, call an electrician.

Why does my security light only work sometimes?

Intermittent operation usually means the PIR sensor is partly blocked, the sensitivity is set too low, or the sensor is detecting movement at the edge of its range. Adjust the angle and sensitivity settings.

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Updated 30 August 2026

Security Light Not Coming On

Your PIR security light is not coming on when it should detect movement.

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What's happening?

PIR (Passive Infrared) security lights detect body heat and movement to trigger illumination. When they stop working, the fault is usually with the PIR sensor, the bulb, the electrical supply, or the settings. Most UK homes have at least one PIR security light above a doorway or driveway.

What usually causes it?

PIR sensor has failed or become misaligned
Bulb has blown (especially halogen floodlights which have a shorter lifespan)
Sensitivity or range setting turned too low
Timer set to a very short duration so the light appears not to work
Spider webs or dirt covering the PIR sensor lens

Is it dangerous?

A non-working security light is not an electrical danger, but it is a security risk. A dark entrance or driveway makes your home more vulnerable to break-ins and increases the risk of trips and falls.

Can I fix it myself?

Start with the obvious: check and replace the bulb. Clean the PIR sensor lens with a damp cloth to remove dirt, cobwebs, and insects. Check the sensitivity and timer dials on the light (usually small adjustable knobs on the unit). Make sure the range setting is not set to minimum and the timer is not set to the shortest duration. Some PIR lights have a manual override — check if it has been switched to the off position.

When should you call an electrician?

Call an electrician if the bulb is fine and the sensor appears clean but the light still does not work, if the light has power but the PIR sensor has failed, or if you want to upgrade to a modern LED security light. If the light is hard-wired (not plug-in), any replacement work should be done by an electrician.