PIR Security Light Not Working: Causes, Checks & Fixes

Stop if there is heat, burning, arcing, exposed parts or water near the light

Do not open fittings, switches or junctions while energised. Isolate the lighting circuit and call a registered electrician where danger signs, water ingress or fixed wiring faults are present.

MOST LIKELY CAUSES

Start with these

Daylight setting The light may be correctly inhibited during daylight.

Sensor aim or obstruction The PIR may not see movement in the intended zone.

Failed lamp or driver The light source may have failed while the sensor still works.

Water or supply fault Outdoor fittings can suffer moisture and cable problems.

◫ Symptom variations Match the exact behaviour before testing. ⌄

Never turns on
Works only in test mode
Works during the day but not at night
Sensor clicks but lamp stays off
Trips the RCD in wet weather

✓ Quick checks Safe checks before opening any fitting or switch. ⌄

Check the lamp or LED module where it is user-replaceable.
Check wall switches, dimmers, pull cords, timers and smart controls.
Inspect the consumer unit for a tripped breaker, RCBO or RCD.
Look for heat, smell, buzzing, water or recent building work.
Attempt one controlled reset only if no danger signs exist.

If operation returns: monitor the light and control.

If the fault remains: leave the affected fitting or circuit off and arrange testing.

1 Fix 1 — Test after dark or cover the sensor Follow this check without opening live electrical equipment. ⌄

Process

Simulate night conditions and trigger movement.

Success looks like: The light operates, confirming settings rather than failure.

Failure means: If not, continue with lamp and supply checks.

2 Fix 2 — Adjust time, lux and sensitivity Follow this check without opening live electrical equipment. ⌄

Process

Set controls to mid-range and aim the sensor correctly.

Success looks like: Reliable detection returns.

Failure means: If no response, the PIR or supply may be faulty.

3 Fix 3 — Power-cycle the fitting Follow this check without opening live electrical equipment. ⌄

Process

Switch off the local isolator briefly if safe.

Success looks like: The sensor resets and operates normally.

Failure means: Persistent failure requires inspection.

⌁ Common causes explained Why the fault may happen. ⌄

A PIR light may fail because of daylight settings, incorrect sensor aim, a failed lamp or LED driver, no supply, water ingress or a faulty PIR sensor.

Lighting faults can be simple lamp failures or signs of loose connections, failed controls and water ingress. Heat, crackling and repeated protective-device operation require prompt investigation.

⌘ Advanced diagnostics Technician-level testing for a competent electrician. ⌄

Verify permanent live, neutral and switched output.
Test PIR relay operation.
Inspect seals and cable entries for moisture.
Check LED driver or lamp module.
Confirm manual override wiring and control settings.

▣ Parts that may need replacing Common failed components linked to this fault. ⌄

PIR sensor
Complete security light
LED driver
Lamp
Photocell
Cable gland or seal

! When to call an electrician Conditions that should end DIY troubleshooting. ⌄

The switch or fitting is hot, burnt, buzzing, crackling or sparking.
A breaker or RCD repeatedly trips.
Water may have reached the fitting, switch or cable.
Several lights are affected and lamp replacement does not help.
The fitting is sealed, permanently wired or mounted at unsafe height.
Recent drilling or building work may have damaged a cable.

? Frequently asked questions Common questions about lighting faults. ⌄

Can a light fail without tripping the breaker?

Yes. Lamps, drivers, switches and local connections can fail while the circuit remains energised.

Why does a new LED lamp still not work?

The driver, dimmer, switch, fitting or circuit supply may be faulty or incompatible.

Is flickering dangerous?

It can be harmless incompatibility, but flickering with heat, buzzing or several affected lights may indicate a loose connection.