Does the interior light work when other doors are opened? Does the light work if turned on manauly?
I'm not sure how the interior lights on a P38 compare to a classic, but on the classics the locking and the lights are seperate. If the light works for other doors then check the wiring and switch to the door(s) that don't work. If the lights don't work at all then it may be a blown fuse/bulb(s), wiring or something in circuit like a relay or diode thats failed.
