Symptoms
- Light doesn't turn on when someone walks by
- Light worked before but stopped responding
- Sensor lens looks dirty, foggy, or is aimed wrong
Likely causes
- CommonSensitivity or range set too lowMost motion sensors have adjustable range and sensitivity dials that can end up set too conservatively.
- CommonA burned-out bulbWorth ruling out before assuming the sensor itself has failed.
- CommonA dirty or fogged sensor lensDust, cobwebs, or condensation can block the sensor from detecting motion.
- PossibleSensor time delay set to a very short durationA very short 'on time' setting can make it seem like the light never comes on if you're not standing right at the sensor.
- PossibleThe sensor's daylight/dusk setting is preventing daytime operationMany motion lights are set to only operate after dark, which is often expected behavior, not a fault.
What to do
- Replace the bulb with one known to work.
- Clean the sensor lens gently with a soft, dry cloth.
- Adjust sensitivity and range dials, usually on the fixture itself, to a higher setting.
- Test at night if the light has a dusk sensor that prevents daytime activation.
- Check the sensor's physical aim, since some can be tilted to cover more or less area.
- Test by walking through the detection zone at different distances to find where it does or doesn't trigger.
- Call an electrician if adjusting settings and cleaning the lens doesn't restore reliable detection.
Tools and parts
- Soft cloth
- Step ladder
When to call a pro
Call an electrician if adjusting the sensor and replacing the bulb doesn't fix reliable triggering.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.