What was found
WHILE ACFT ELECTRICAL WAS POWERED ON GROUND WITH GPU, SMOKE DETECTED COMING FROM LOWER LOUVERS BENEATH AFT EQUIPMENT BAY ALONG WITH A STRONG ELECTRICAL BURNING ODOR. SUBSEQUENTLY EXTERNAL POWER WAS DISCONNECTED, BATTERY WAS DISCONNECTED AND ALL ELECTRICAL (AVIONICS, AIR CONDITIONING, & NAV LIGHTS) TURNED OFF. ON INSPECTION IN EQUIPMENT BAY, SMOKE COULD BE SEEN BUT SOURCE COULD NOT BE DETECTED. SMOKE ABATED WHEN ELECTRICAL POWER DISCONNECTED. TURNED ON AIR CONDITIONING & FOUND SPARKS COMING FROM ARMATURE & BRUSH AREA. R & R AIR CON MOTOR. SERVICE OF AIR CON SYSTEM. AIR CON SYSTEM OPS & LEAK CHECKED GOOD IAW MM 21-52-00.