What was found
(CAN) ON APPROACH, WHILE DESCENDING THROUGH 8000 FT THE CREW NOTED ILLUMINATION OF THE CABIN DOOR WARNING LIGHT. THE BLEEDS WERE TURNED OFF AND THE CABIN DEPRESSURIZED. JUST PRIOR TO LANDING THE LIGHT EXTINGUISHED. UPON EXITING THE AIRCRAFT, THE CREW VERIFIED THAT THE DOOR WAS INDEED IN THE CLOSED AND LOCKED POSITION AND THAT ALL VISUAL LOCK INDICATORS ON THE DOOR WERE SHOWING A GREEN/LOCKED INDICATION. MAINTENANCE INSPECTION DETERMINED THAT THE CABIN DOOR CLOSED SWITCH MOUNTED ON THE FORWARD LOWER DOOR FRAME WAS JUST BARELY BEING MADE. THE SWITCH WAS ADJUSTED FOR PROPER OVER TRAVEL AND THE DOOR WARNING SYSTEM VERIFIED FOR CORRECT OPERATION. IN ADDITION THE DOOR LATCHING MECHANISM AND STRUCTURE WAS INSPECTED.