What was found
NR 2 ENGINE FIRE DETECTION WILL NOT TEST IN NORMAL POSITION. WHEN SELECTED TO B LOOP LIGHT REMAINS ON AND WARNING HORN REMAINS ON. A LOOP OPERATIONS NORMAL. GROUNDED-YES. ACCOMPLISHED T/S, PER B737-900 FIM 26-10 TASK 811 - REFERENCE B737-900 IPC 26-11-02-01A SHEET 017 - AT 11:00 POSITION ON CORE FOUND MW0326 HARNESS CHAFED THROUGH TEFLON INSULATOR ON CLAMP AND TO HAVE WORN THROUGH MORE THAN HALF THE DIAMETER OF THE HARNESS. WITH P8-1 PANEL SET TO LOOP B ONLY, NR 2 ENGINE FIRE WARNING WOULD SOUND. REMOVED AND REPLACED TEFLON INSULATOR. RECONFIRMED FAULT, NR 2 ENGINE CORE FIRE DETECTOR HARNESS MW0326, AT 11:00 POSITION HAS A DETECTOR CHAFED THROUGH MORE THAN 1/2 DIAMETER. REMOVED & REPLACED MW0326 CORE FIRE DETECTION HARNESS, REF B737-900 AMM 26-11-02-400-802. OPERATIONS CHECK NORMAL, REF AMM 26-11-00-710-801. REPOSITIONED NR 2 OVERHEAT DETECTION SWITCH TO NORMAL POSITION.