What was found
APU FIRE WARNING INDICATION. RTFL. CREW SAID THAT AT TOP OF CRUISE APPROX 1HR 30 MIN INTO FLT THEY HEARD CLICKING FROM THE FIRE PANE L FOLLOWED BY APU FIRE MSG AND AND HANDLE LITE, FIRED BOTTLE, LITE WENT OUT BUT CLICKING FROM PANEL CONTINUED FOR ANOTHER 30 MINUTES BEFORE STOPPING. LANDING WEIGHT WAS 929.7 AND FUEL ON BOARD WAS 142.1 AT THE GATE. FOUND WIRES CHAFING UNDER CLAMP IN APU COMPARTMENT FOR T1814 'A' LOOP. REPLACED W720-451- 18 AND W720-452-18 PER WDM 26-15-11. TEST NORMAL. NO EVIDENCE OF FIRE NOTED.