Motion sensor garden light not working

[greenchicken]

Just moved into new house and this garden motion sensor light can only be turned on and off from the wall switch (inside). There are two small dials on the bottom which I assume control the motion range and time, but twiddling them doesn't seem to make any difference. Is the motion sensor likely broken/is there a way to replace it?

Can't find a brand name/model number to seek out the manual.

Thanks

 

[JohnD]

the PIR looks very old and faded, perhaps it has failed. The lamp appears to be the LED type that is not serviceable. you have to block the light sensor before it works automatically.

You can buy a replacement general-purpose PIR but I don't know if it would be better value than a complete new lamp.
example

example

the square box on the wall is probably a weathertight junction box that you can retain. This makes it fairly easy to swap the lamp.

https://www.tlc-direct.co.uk/tcl/search?query=pir&Submit=Search

you may find one cheaper in Aldi, Lidl or ebay

 

[Harry Bloomfield]

PIR lens looks discoloured, as if water has got inside.