How To Fault Find A PIR Sensor


If you're having trouble setting a PIR sensor, you will find this thorough diagnosis guide helpful.

Modern PIR sensor technology has come a long way in recent years, so if you're having problems with one its very likely one or more of the setup issues below will be the key to getting the unit behaving correctly. The same remedies should apply whether you are setting up a standalone PIR or a light fitting with a PIR integrated into it.

Fault Cause Remedy
Light Stays On Wiring incorrect Check wiring supply to the device and to the BLACK wire side of the terminal block, the brown wire is a switched output
Light Stays on Detecting heat movement Cover sensor completely with tin foil or other solid material. If the sensor goes off after time delay period it is detecting a moving heat source
Light Stays on Detecting heat movement Switch off and switch back on to reset
Light Stays on (Photocells) Too Dark Sensor is located in an area that does not get sufficient light for the sensor to switch off the lighting
Light Stays off No power to the unit Check power supply, fuse, MCB and also that the unit is switched on
Light Stays off Lamp has failed Check the condition of the lamp and ensure the lamp is correctly seated
Light Stays off Too much ambient light Check for external light sources and photocell setting
Light works on day/test mode but not at night Too much ambient light Check for external light sources and photocell setting
Light only works when very close to it (within 300mm)

  1. Shrouds have been fitted.
  2. Too much ambient light.
  3. Remove shrouds
  4. Check for external light sources and photocell setting

Only getting 3-4 metres detection

  1. Approaching directly towards sensor
  2. Mounted too high