A B737-200 CAPT'S ALTIMETER WAS REPLACED TO CORRECT A PRESSURIZATION RPT. ACFT OVERNIGHT WITH AUTOPLT AND TCASII RPTS. DISCOVERED INCORRECT CAPT'S ALTIMETER INSTALLED.

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REF LOG PAGE X ACFT ARRIVED WITH AN OFF SCHEDULED DSCNT LIGHT ILLUMINATED FOR NO APPARENT REASON. DURING TESTING OF CABIN PRESSURIZATION SYS DURING THE NIGHT; CAPT'S ALTIMETER FAILED STEP E. (E)(6)(7) AUTO MODE BAROMETRIC CORRECTION CIRCUIT TEST. A TOTAL OF 3 TECHNICIANS INCLUDING MYSELF WERE WORKING THE DISCREPANCY AND ONE OF THE TECHNICIANS WORKING WITH ME; WENT IN AND GOT A B737-200 ALTIMETER PART NUMBER X AND INSTALLED IT INTO THE CAPT'S SIDE. I WITNESSED THE INSTALLATION OF THE ALTIMETER AND THE OPS CHK PER THE MAINT MANUAL. THE PRESSURIZATION TEST THAT FAILED PASSED AND WE CONTINUED ON WITH THE REST OF THE OPS CHK. IT WAS MENTIONED THAT THE IPC (ILLUSTRATED PARTS CATALOG) NEEDED TO BE CHKED BEFORE WE FINISH. LATER THE END OF THE PRESSURIZATION TEST FAILED AND WE STARTED CHANGING THE PRESSURE CTLR AND OVERHEAD CTL PANEL OUT WITH NO HELP AND TIME RUNNING OUT TO COMPLETE PUTTING THE ACFT BACK TO NORMAL AND FINISHING PAPER WORK BEFORE THE END OF THE SHIFT. I OR WE FORGOT TO CHK THE IPC FOR VERIFICATION THAT THE B737-200 ALTIMETER; PART #X; INSTALLED WAS APPLICABLE FOR ACFT X. ACTUALLY THE CORRECT PART NUMBER WAS Y; WHICH WAS INSTALLED ON LOG PAGE X FOR ANOTHER PROB; WHICH THE INCORRECT PART NUMBER ALTIMETER INDUCED. SINCE I WAS DOING THE PAPERWORK AND WITNESSED THE INSTALL/OPS CHK OF THE ALTIMETER; I SIGNED OFF ON THE INSTALL TO SPD UP THE COMPLETION OF PAPERWORK. LATER THAT NIGHT; ACFT X RETURN TO ZZZ FOR OVERNIGHT STAY WITH A TCASII DISCREPANCY AND A SCHEDULED AUTOPLT WORK CARD. THE TCASII WAS TROUBLESHOT WITH POSSIBLE AIR DATA COMPUTER AT FAULT; AND THE AUTOPLT WORK CARD FAILED DUE TO DADC INTERFACE FAULT. BITE CHKING THE AIR DATA COMPUTERS SHOWED THAT BOTH AIR DATA COMPUTERS WERE NOT BITE CHKING NORMAL AND WERE BOTH POSSIBLY BAD. AT THIS POINT; THE ONLY AIR DATA COMPUTERS WE HAD WERE IN ZZZ1 AND WERE ENRTE TO ZZZ FOR THE DISCREPANCY. DAYSHIFT AVIONICS TIED IN AND FOUND LATER IN THE DAY THE INCORRECT ALTIMETER PART NUMBER WAS INSTALLED ON THE CAPT'S SIDE; WHICH WAS CAUSING THE TCASII TO FAIL AND AUTOPLT WORK CARD TO FAIL. UPON INSTALL OF THE CORRECT PART NUMBER ALTIMETER; THE TCASII AND AUTOPLT WORK CARD OPS CHK GOOD. THAT NIGHT WHEN I CAME IN AND CHKED MAINT COMPUTER FOR WHAT FIXED ACFT X. I FOUND OUT WHAT HAPPENED AND FILLED OUT THIS ASAP FORM.