What was found
APU FIRE WARNING WHILE APU WAS RUNNING. PULLED FIRE HANDLE AND DISCHARGED BOTTLE. WARNING CONTINUED INTERMITTENTLY FOR APPROXIMATELY 8 MINUTES AND STOPPED. INSPECTED APU AREA, NO SIGN OF FIRE. PLACED ON MEL 26-08-01. NOTICED WIRING AT FWD AND AFT ENDS OF APU UPPER SHROUD HAD BEEN REPAIRED AND WAS CONTACTING STRUCTURE. UNABLE TO DUPLICATE WARNING BUT SUSPECT SHORT TO STRUCTURE. ADJUSTED ROUTING OF WIRES.