P.I.R. Puzzle

[Shutpa]

We have 2 pir lamps, one installed by the original builder and a second installed by the builder who carried out our extension 15 years ago. The original one has a switch and when that switch is in the 'off' position, the pir will not function. However, the newer light does not work in the same way. If I see that the light is on, i can switch it off regardless of the position of the switch 'on' or 'off'. And having done so, the light is only off until someone or something causes it to light again by activating the pir sensor. In other words, I cannot switch this light off permanently even if I wanted to. Can someone throw some light (excuse the pun) on this please?
Strange as it may seem, we have only discovered this recently because we rarely use the door that the newer light protects.

 

[stillp]

If I see that the light is on, i can switch it off regardless of the position of the switch 'on' or 'off'.

Can you explain that in a bit more detail please?

 

[Shutpa]

Hi and thanks for your rapid reply. If the light is activated via the sensor I can switch it off regardless of the position of the switch, up or down. Immediately after switching it off, the light will come on again if activated by the sensor and I can again switch it off by flicking the switch again this time in the opposite direction. The light does go on and off as it should do without even touching the switch but the latter can be on or off in either the up or down position.

 

[stillp]

Sounds to me as if somebody has swapped Line and Switched Line at the lamp. Do you have a multimeter?

 

[Shutpa]

Dont have a meter. Would a pic of the switch box innards be any use?

 

[stillp]

Not really. Get yourself a multimeter tomorrow, they're only the price of a couple of pints (or Starbucks coffees if you prefer).

 

[Shutpa]

Ok. Will do. What will it tell me?

 

[stillp]

You should be able to identify which conductor is the Line feed to the switch and which is the Switched Line to the lamp.

 

[ban-all-sheds]

Ok. Will do. What will it tell me?

http://www.google.co.uk/search?q=multimeter+101

 

[Shutpa]

Sorry guys, have given you a bit of wrong info. When the switch is in the 'off' position, the pir sensor operates as it should do. When it is in the 'on' position, the light is continually on. Now I can easily access the switched line to the lamp and can just as easily fit a new switch to this line which in effect would provide me with a means of switching the lamp completely off, something I don't have at the moment. However, if I do fit that switch and leave the rocker on the 'on' position, I still have the original switch in place with the pir system in the 'off' position and the continuous light in the 'on' position and I am not happy with that. Ideally, I would like to dispense with 'always on' down position of the original switch and replace it with the more conventional off/on function. I have identified the cable from the lamp to the switch.

 

[EFLImpudence]

Then it works as intended.

You will have at the switch terminals:

O 'Supply live' and 'feed to PIR'

O 'feed to light for perm.on'

To do what you want, you need to remove 'feed to light for perm.on' and terminate safely.
Move 'feed to PIR' to bottom terminal

 

[Shutpa]

Then it works as intended.

You will have at the switch terminals:

O 'Supply live' and 'feed to PIR'

O 'feed to light for perm.on'

To do what you want, you need to remove 'feed to light for perm.on' and terminate safely.
Move 'feed to PIR' to bottom terminal

Thank you. Job done and happy now. Don't know why the light was fitted as it was in the first place. The frightening thing is that a friend changed the lamp a few years back with just the switch in the up position.