What was found
(CAN) DURING TRAINING, FLT INSTRUCTOR NOTICED LEFT ENGINE TEMP GAUGE PEGGED AT HIGH RED LINE. PREVIOUS SCANS OF INSTRUMENTS, BY BOTH STUDENT AND INSTRUCTOR HAD NOT INDICATED ANY PROBLEM. LOWER POWER SETTING TRIED BUT DID NOT DECREASE THE TEMP: PILOT MADE DECISION TO SHUT DOWN ENGINE TO AVOID DAMAGE AND HEADED INBOUND TO FIELD (YQM). A/C LANDED WITHOUT FURTHER INCIDENT. ENGINE GROUND RUN SERVICEABLE, BUT DECISION MADE TO INSPECT FURTHER. WIRE FROM INBOARD OF NACELLE, TO TEMP SENDER REMOVED FOR INSP. WIRE FOUND CHAFED 8 INCHES FROM SENDER. IT RUBBING ON ENGINE MOUNT OBSTRUCTED BY TY-RAPS ATTACHING IT. WIRE REPLACED, ISOLATED AND ACFT RETURNED TO SERVICE