What was found
REPORT OF APU FAULT 49-41011, NO FLAME SHUTDOWN. ACFT GROUNDED. REMOVED AND REPLACED THE IGNITION UNIT AND IGNITOR PLUG IAW AMM 49-41-31, AND 49-41-51. AFTER REPLACEMENT OF IGNITION UNIT AND IGNITOR, APU SHOWED FAULT LIGHT ON START. APU BITE CHECKED IAW FIM 49-61, TASK 801 SHOWED CURRENT STATUS FAULT 49-31160 "FCU RESOLVER CIRCUIT SHOWS OPEN" AND SAME FAULT HAD BEEN LOGGED IN MAINTENANCE HISTORY FAULT MEMORY FOR EACH OF THE LAST 18 STARTS. ACCOMPLISHED FIM 49-32 TASK 802 FOR FAULT 49-31160 - ACCOMPLISHED RESISTANCE TESTS AT APU FCU CONNECTOR P22 PINS 2 AND 3 AND AT APU FIREWALL CONNECTOR D10436 PINS 12 AND 26 - RESISTANCE IN BOTH CASES WAS 72 OHMS - WITHIN FIM LIMITS. CLEANED AND REINSTALLED CONNECTORS AND OPERATED APU - NO FAULTS SHOWED IN CURRENT STATUS.