What was found
(CAN) AC WAS SITTING ON RAMP WITH GROUND POWER ATTACHED TO AC, AC MASTER SWITCH ON. SMOKE ORIGINATING FROM LOWER SIDE OF IB SECTION OF RT WING. CREW WAS NOTIFIED, AC WAS POWERED DOWN ELECTRICALLY, GPU REMOVED. SMOKE STOPPED WITH POWER OFF, VERIFIED TO BE COMING FROM RT WHEEL WELL. CAUSE OF SMOKE WAS QUICKLY ISOLATED TO LANDING LIGHT SAFETY SWITCH IN RT MAIN GEAR WELL. THIS PLUNGER TYPE SWITCH IS ACTIVATED BY GEAR DOOR, UPON RETRACTION, REMOVES POWER SOURCE TO LANDING LIGHT AS BACK UP TO COCKPIT SWITCH. NORMALLY POWER IS ALWAYS APPLIED THROUGH THIS SWITCH. FAULT WAS ISOLATED TO SWITCH ONLY, WITH NO ASSOCIATED HEAT DISTRESS TO AC OR TO WIRING. AC ELECTRICAL SYS WAS VERIFIED SERVICEABLE, SWITCH REPLACED.