What was found
(CAN) WHILE AIRCRAFT WAS IN CRUISE, THE FIRE INDICATOR LIGHT FOR THE LT ENGINE ILLUMINATED. THE PILOT RELEASED THE RETARDANT LOAD, THROTTLED THE ENGINE BACK AND SHUTDOWN THE ENGINE. WHEN THE ENGINE WAS SHUTDOWN THE WARNING LIGHT EXTINGUISHED. THE AIRCRAFT RETURNED TO BASE. DURING INVESTIGATION BY MAINTENANCE THE FIRE DETECTOR WIRE WAS INDICATING A PARTIAL SHORT. THE FIRE DETECTOR WIRE WAS REPLACED AND THE AIRCRAFT WAS RETURNED TO SERVICE.