[ark123]

If you say it is dim and when you use the camera it goes full light then most likely disabling it will not help you. It sounds like your phone has it's electronic component failure when it doesn't shut fully. (like leaking water tap).

P.S. If you don't have warranty (most likely it won't cover your phone anyway because of the water damage) and you want to preserve the phone battery then the only way to do it will be to physically remove the LED.