What was found
DURING POST FLIGHT INSPECTION, 4 MINUTES AFTER POWERING THE EMERGENCY INSTRUMENT LIGHTS, THE PILOT SAW SMOKE ASSOCIATED WITH A BURNING ODOR COMING FROM THE LEFT MASTER WARNING LIGHT SWITCH. SYSTEM WAS POWERED DOWN. MAINTENANCE INSPECTED THE SWITCH AND WIRE BUNDLE. WIRE BUNDLE HAD NO DEFECTS NOTED. MASTER WARNING SWITCH WAS NOT SECURED ALL THE WAY IN SOCKET CAUSING ARCHING. SECURED THE SWITCH ASSEMBLY. OPS CHECKED GOOD. NO DEFECTS NOTED. AIRCRAFT WAS RETURNED TO SERVICE.