Outer Limits 4x4 Board

Heres a challenge. My park lights are shorting out and turning themselves on, when the ignition is off. As soon as the ignition is switched on they turn off (without fail). But when the ignition is on and the headlights are on the interior light has a dull glow when in the door position. It dosent happen very often, just every now and again. I reckon it must be corroded wires somewhere (has been half drowned in salt water) but where? Any ideas?

What sort of vehicle is it & have you checked the earths at all?