Or a covid mask (black)An old, suitably large glove sometimes works as well.
Looks like it could be a mains siren (not SA), or a daylight sensor (for outside lighting).photocell for outside lighting
Thanks for the warning. The garage has its own consumer unit (which can itself be isolated from the house). As the wiring for the property is old and a bit inconsistent I will check nothing is live before removing the sensor.Be very careful when disconnecting it as I would assume that its 3 core flex going into it and what should be the earth cable will more than likely be the switched live !
I mulled one to get the connector. Soldered three wires on to it. Wago across L-S/L , one on N. Enables you to test supply, load test etc. I also have a much rarer OEM shorting plug. I’ll post pics later if I can be motivated enoughor since they almost always fail on, keep a dead one spare... or solder a bit wire between SL & L on a spare