What was found
(CAN) IN CRUISE FLIGHT AT 5000 FT, TAIL ROTOR GEARBOX HOT/CHIP LIGHT CAME ON. FLIGHT CREW ASKED FOR AND RECEIVED IMMEDIATE DESCENT INTO CYYJ. THE AIRCRAFT LANDED AND WAS SHUTDOWN NORMALLY. THE ENGINEER REMOVED CHIP PLUG AND FOUND NO METAL. WHEN REINSTALLED THE CAUTION LIGHT CAME ON AGAIN. A NEW TEMP/CHIP PLUG WAS INSTALLED. NO CAUTION LIGHT CAME ON. THE AIRCRAFT WAS GROUND RUN AND LEAK CHECKED AND NO FAULT FOUND. THE AIRCRAFT WAS RETURNED TO SERVICE.