The Sun Can Trigger Motion Sensors
My Motion Sensor triggers when there is no motion. Could the heat from the sun be triggering it?
Yes, it is possible for the sun to trip a motion sensor through direct or reflected light.
Likewise, an object within the view of the motion sensor that becomes heated by the sun, or is itself heated somehow (i.e., car engine, heat vent) can generate false motion detection.
It is best to mount the motion sensors so that they are looking slightly downward to avoid being triggered by sunlight.