What was found
HAD A BURNING ODOR IN THE COCKPIT AND CABIN WHILE OPERATING BLEED AIR HEAT AND ON APPROACH. LANDED, A VISUAL INSPECTION OF THE MAIN TRANSMISSION AND TRANSMISSION DECK AREA REVEALED THAT THE AIR CONDITIONING DRIVE BELT WAS BROKEN FROM THE DRIVE PULLEY FOR THE 90 DEGREE GEARBOX WAS MELTED CAUSING THE BURNING ODOR IN THE COCKPIT AND CABIN. ALL PIECES OF THE DRIVE BELT WERE RETRIEVED AND AREA INSPECTED FOR FOD. AREA WAS CLEARED OF ALL DEBRIS. AIR CONDITIONING SYSTEM WAS DEACTIVATED. PERFORMED GROUND RUN, NO DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE.