What was found
(CAN) DURING FLT A/C EXPERIENCED FLICKERING LT WING BODY OVERHEAT INDICATION WITH INCREASING FREQ. OVERHEAT LIGHT ILLUMINATED OFF & FLICKERED ON & OFF CONTINUOUSLY WHEN LT ENGINE BLEED VALVE & ISOLATION VALVE WERE CLOSED (WITH APU OFF). FLT CREW CONTACTED MCC & CYCLED VALVES WITH NO RESOLVE.DUE TO ICING CONDITIONS ENROUTE & INABILITY TO CONFIRM BLEED AIR WAS ISOLATED - A/C WAS DIVERTED TO FOR PRECAUTIONARY LDG. FLT CREW PERFORMED ENGINE RUNS & COULD NOT FAULT. MAINT CALLED OUT TO INSPECT - INDICATION PROBLEM WAS ISOLATED TO A SEVERELY CHAFED WIRE IN APU AREA OF OVERHEAT LOOP. TEMP REPAIR CARRIED OUT.A/C RT-SRV WITH NO FURTHER INCIDENTS TO REPORT.