For you notice the PIR not activating correctly, it no longer detects or does not operate at the correct time then you can do a PIR reset if your PIR has the required adjustment dials:

1. Turn off the power to the item

2. Adjust all PIR adjustment dials to the MINIMUM setting (most models fully anticlockwise but check the manual of your model to be sure)

3. Turn on the power to the item - it will light up and leave for 5 minutes 

4. Turn the PIR adjustment dials back to the required setting.

This should help reset the PIR.