What was found
LANDED UNDER AMBER ALERT. EN ROUTE TO MSP, RECEIVED APU FIRE WARNING INDICATION. EXTINGUISHER USED. *S/D* VISUAL INSPECTION OF APU INDICATED NO SIGNS OF FIRE. VISUAL INSPECTION OF WIRING AND LOOPS IN APU COMPARTMENT AND AREA FORWARD OF BULKHEAD SHOWED NO SIGNS OF DAMAGE, CHAFING, OR BREAKS. WIRING TROUBLESHOOTING ISOLATED CAUSE OF FIRE INDICATION TO M717 APU TAILPIPE LOOP (AT CONNECTOR D4934, REF WDM 26-12-11). M717 LOOP AND APU FIRE EXTINGUISHER BOTTLE WERE REPLACED, AND THE AIRCRAFT WAS RETURNED TO SERVICE. ALSO REFERENCE MRR 99UAL900399.