What was found
(CAN) DURING HEAVY MAINT INSPECT FOUND TWO WIRES CHAFED & BROKEN AT DETERIORATED CLAMPS IN LOWER AFT FIREWALL AREA. RUBBER CUSHION HAD TORN AWAY ALLOWING METAL CLAMP TO WEAR WIRES. THESE WIRES ARE FOR FIRE LOOP SYSTEM ON NR 3 ENGINE, WHICH WAS WORKING WHEN AIRCRAFT WAS TAKEN DOWN FOR MAINT. ONLY SUPPORT CLAMPS WERE HOLDING WIRES TOGETHER. FIRE LOOP SYSTEM HAS BEEN SNAGGED MANY TIMES IN THE PAST, IT WOULD FAIL PRE-FLIGHT TEST THREE OR FORE TIMES PER YEAR, MOSTLY ON COLD WINTER MORNINGS. IT WAS USUALLY REPAIRED BY CLEANING/REPLACING CONNECTIONS IN THE FIRE LOOP. I SUSPECT THAT THE BAD CONNECTION IN THESE CHAFED & BROKEN WIRES MAY HAVE INCREASED THE RESISTANCE IN SYSTEM AND CAUSED TEST TO FAIL IN THE SYSTEM.