What was found
ON GROUND WITH GPU POWER CONNECTED, ODOR OF ELECTRICAL SMOKE NOTICED IN COCKPIT. SMOKE INTENSIFIED TO VISIABLE HAZE & SHUTDOWN ALL SYS, AVIONICS POWER AND EXITED ACFT. ONCE OUTSIDE, SAW SMOKE COMING OUT OF AFT EQUIPMENT BAY (HELL HOLE) VENTS. OPENED AFT BAGGAGE DOOR & HELLHOLE ACCESS DOOR, NOTICED THICK SMOKE. FOUND A/C MOTOR LOCKUP. WHILE IN THE PROCESS OF INSTALLING NEW MOTOR FOUND WIRING TO HOUR METER BURNED INSIDE HOUR METER. FAN WAS ALSO BURNED.