What was found
FLT 0843 DURING CRUISE RECEIVED ECAM WARNING AP AUTOTHRUST YAW DAMPER 2 FAULT A/C "ALT LAW", DIVERTED TO ABQ. MAINTENANCE DOWNLOADED PREFLIGHT REPORT AND FOUND BOTH THE NR 2 AND 3 AIR DATA INERTIAL REFERENCE UNITS (ADIRU) FAILED. REMOVED AND REPLACED THE NR 3 ADIRU AND PLACED THE NR 2 ADIRU, COND. 4, NR 2 IR INOP. BITE TEST OF NR 3 ADIRU GOOD. MAINTENANCE REPLACED THE NR 2 ADIRU, SYSTEM OPS TEST WAS GOOD. VENDOR BENCH TEST OF ADIRU CONFIRMED FAILURE OF UNIT; IDENTIFIED REASON FOR FAILURE AS SLOW IGNITION GYRO. REPLACED SENSOR ASSEMBLY AND PERFORMED THERMAL CALIBRATION; FUNCTIONAL TEST WAS GOOD. VENDOR BENCH TEST OF ADIRU WAS NO FAULT FOUND; UNIT WAS THERMAL CALIBRATED, TESTED, AND RETURNED TO SERVICE.