Did you try earthing the switch wire directly to the chassis and see if the light comes on (I'm assuming it's earth switched)? If that doesn't work next thing would be check for continuity of that wire up to the clocks. If that's good, might be time to take it to the instrument repairer.
The N light is very dull at the best of times but I'm sure you would have made extra sure in a dark place.
Good luck and welcome aboard