The behavior of your wall spotlight with motion detector, which goes on and off randomly at night in winter, can have several causes. Here are a few common reasons and troubleshooting tips:
Temperature sensitivity
Motion detectors, especially PIR sensors (passive infrared), react to temperature differences. In winter, the environment is cold and if an animal walks past, for example, the light can often switch on and off because the sensor interprets the movement as “new”. Even if you open a window nearby, the motion detector may be triggered.
Reflections due to snow or ice
Snow or layers of ice on the sensor or in the surrounding area can reflect infrared radiation, causing the sensor to detect movement “incorrectly”.
Incorrect setting of the sensor
Some motion detectors have sensitivity and delay settings. If the sensitivity is too high, it reacts to the smallest movements or temperature fluctuations. If the delay time is too short, it switches on and off quickly.
Lighting conditions and twilight sensor
The twilight sensor on the motion detector may be incorrectly calibrated or “confused” by light reflections, e.g. from car headlights.
Sources of interference / electromagnetic interference
Sometimes electromagnetic interference or an unclean power supply can also lead to irregular behavior.
Defective motion detector
If the sensor is old or faulty, this can also lead to sporadic switching on and off.
What can you do?
Clean the sensor (glass cover) to remove snow, ice and dirt.
Adjust the sensitivity and delay time on the motion detector.
Check the position of the motion detector (e.g. watch out for animals, no windows or reflective surfaces in the detection area).
Check whether a stable power supply is available.
Replace the sensor if necessary or change to a model with better cold/weather resistance.