What was found
FL390 A/S & ALT DISAGREE INDICATIONS WITH A/S & ALT FLUCUATIONS. DETERMINED CA SIDE WAS THE BAD SIDE. INDICATIONS CONTINUED THROUGH DESCENT. NO OVERWEIGHT LANDING.<[01] REMOVED AND REPLACED AIR DATA MODULE ON THE LH CAPT SIDE IAW AMM 34-21-01;[02] I DID NOT REPLACE THE AIR DAT MODULE I REPLACED THE AIR DATA INERTIAL REFERENCE UNIT (ADIRU) CAPT SIDE IAW AMM 34-21-01;[03] R&R CAPT PITOT AIR DATA MODULE PER AMM 34-21-04. REF TTG8Q00RWGS0 FOR OTHER R&R PARTS. AIRCRAFT RECERTIFIED TO CAT III STATUS PER MT 734-00-03 VERIFICATION # 40200.;[04] ALSO REF TO LOG PAGE 2738308 FOR CAT 3