Make sure that you have the replacement spare part available.
If the sensor is damaged, replace it
with a new one.
Switch off both AC (mains) power switch and battery switch.
Make sure that there is no AC (mains)
power available for the system.
Disconnect the cable from the sensor.
Remove the sensor and replace it with a new one.
Connect the cable to the sensor.
If the viewing direction of the background luminance sensor needs fine-tuning, adjust
it by turning the mounting bracket of the sensor. Tighten the screws after the
adjustment.
LM21 mounting requirements
Property
Description
Orientation
Avoid direct and reflected
sunlight into the sensor