Scirocco Central

wondering when the boot light should come on, does it work via a light sensor or should it be in every time the boots open regardless? I'm having no problems with the other courtesy lights so I assume the circuit in general is fine.
It seems to work some days and not others, the bulb's ok I tested that but now I'm wondering where the switch or contacts are so I can check they're ok, are they around the boot catch ?
Anyone else having this issue?
Thanks for looking

My boot light comes on when boot is opened. Goes off after a while if the boot is left open. The switch is in the lift up part of the boot- part of the lock.