My newly installed motion-sensor security flood light would stay on after being turned on by a motion event. I kept thinking there must be some kind of mammal animals with body heat like rats that it was detecting continuously. After a month, I determine that I have installed the flood light incorrectly. The motion sensor is picking up the heat from the light bulb because it’s too close to the motion sensor. Below is the original installation of the flood light. Notice how close the bulbs were to the motion sensor.

By flipping the L-arm to the opposite direction (see below picture), now the light would stay on exactly for the 1-/5-/10-minute duration I set it to be (normally 1 minute to save electricity):

Note how it’s set up in the original box:

My lessons learned: follow the directions and check the manual. In the manual, it’s clearly stated that lamps need to be kept at least 1″ from the sensor and the trouble shooting guide has this issue identified as the possible cause.


Appendix: Heath Zenith SL-5412 Manual