What was found
TCAS FAIL, BOTH CHANNELS. DEBRIEF WITH CREW, TCAS FAILED AT 15000 FT, CREW PUT IN ALT, 1 & 2, NO HELP. NO MSSG AT THIS TIME. TCAS STATUS MESSAGE PRESENT, NOT ACTIVE ON MAT. FAULT INTERMITTANT IAW FIM 34-21 TASK 848. RECOMMEND REPLACE ADIRU IAW FIM DUE TO HISTORY. R & R AIR DATA INERTIAL REFERENCE UNIT IAW AMM 34-21-01. PERFORMED SOFTWARE LOAD ON NEW ADIRU IAW AMM 34-21-01-420-801. VERIFIED OPS CHK & OPS SOFTWARE CORRECT. PERFORMED TCAS GROUND TEST IAW AMM 34-45-00-740-801. OPS CHKD GOOD. PERFORMED TCAS COMPUTER BITE ON TCAS BOX, NO FAULTS. STATUS MESSAGE CLEARED ITSELF & DID NOT RETURN DURING OPS CHECKS. NO FURTHER FAULTS PRESENT. OPS CHKD TCAS AND ADIRU GOOD.