What was found
ENROUTE, AFTER TAKEOFF TAIL COMPARTMENT TEMPERATURE HIGH LIGHT ILLUMINATED, FOLLOWED BY LOUD RUMBLING IN TAIL COMPARTMENT. RETURNED, WHEN LIGHT FAILED TO EXTINGUISH. EXTINGUISHED OF SHORT FINAL. LANDED WITHOUT INCIDENT. REPLACED RT PACK AND CROSSOVER WYE DUCT. SYSTEM GROUND CHECKED NORMAL OPERATION.