AN AIRBUS 320 ON TKOF DIVERTED DUE TO INABILITY TO RETRACT THE NOSE GEAR ON FIRST ATTEMPT; SECOND OK. FOUND NOSE GEAR POS SENSOR AND TARGET OUT OF ADJUSTMENT.

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ACFT LANDED IN ZZZ ON THE MORNING OF FEB/SUN/03. AN ECAM MESSAGE FOR THE LNDG GEAR SHOCK ABSORBER (NOSE LNDG GEAR) NOT EXTEND APPEARED AFTER ENG SHUTDOWN AT THE GATE. THE ACFT WAS REMOVED FROM SVC AND MOVED TO THE HANGAR FOR TROUBLE-SHOOTING. DAY SHIFT MECHS BEGAN TROUBLE-SHOOTING THE ACFT PER AIRBUS TROUBLE-SHOOTING MANUAL; 32-31-00-810-868. DURING THIS INSPECTION AND TROUBLE-SHOOTING THE LINK ASSEMBLY ATTACHING TO THE TARGET FOR PROX SENSOR 25GA WAS DETERMINED TO HAVE A BAD BEARING ON THE LOWER END. THE LINK WAS REMOVED AND A REPLACEMENT ORDERED. WHEN I ARRIVED TO WORK ON THE EVENING OF FEB/SUN/03; I WAS ASSIGNED TO REPLACE THE LINK AND CONTINUE THE TROUBLE-SHOOTING MANUAL TO LTS END; I WAS ASSIGNED TO COMPLETE THIS TASK WITH 1 OTHER MECH (18 YRS EXPERIENCE). THE NEW LINK ARRIVED AT THE START OF OUR SHIFT. THIS LINK ASSEMBLY IS FIXED IN NATURE AND HAS NO ALLOWANCE FOR ADJUSTMENT. WE INSTALLED THE NEW LINK USING THE ILLUSTRATED PARTS CATALOG 32-21-11; PAGE 14; AS OUR REF. AFTER INSTALLATION; THE ASSEMBLY WAS INSPECTED BY A QUALIFIED INSPECTOR FOR SAFETY AND SECURITY. AT THIS POINT WE JACKED THE ACFT NOSE LNDG GEAR FOR A FUNCTIONAL TEST OF THE NORMAL EXTENSION AND RETRACTION OF THE NOSE LNDG GEAR. THIS WAS THE LAST STEP IN THE TROUBLE-SHOOTING MANUAL. ALL OTHER STEPS IN THE TROUBLE-SHOOTING MANUAL HAD BEEN COMPLETED BY THE DAY SHIFT MECHS. DURING THE TEST OF THE NOSE LNDG GEAR; IT RETRACTED NORMALLY DURING THE FIRST ATTEMPT. THE TEST REQUIRES THE NOSE LNDG GEAR FUNCTIONAL TEST TO BE PERFORMED TWICE TO ALLOW FOR TESTING OF THE SECOND LNDG GEAR CTL UNIT. ON THE SECOND ATTEMPT; THE LNDG GEAR WOULD NOT RETRACT. SEVERAL ATTEMPTS WERE MADE WITH THE SAME RESULT. A FAILURE OF LNDG GEAR CTL UNIT 2 TO ALLOW FOR RETRACTION. THIS WAS NOTED (A WRITE-UP AGAINST THE ACFT WAS MADE). END OF SHIFT. DAY SHIFT CONTINUED AND WERE ABLE TO COMPLETE THIS TASK; AND THE ACFT WENT INTO SVC. ON DEP FROM ZZZ; THE GEAR FAILED TO RETRACT ON THE FIRST ATTEMPT. RETRACTED NORMALLY ON THE SECOND ATTEMPT. THE ACFT WAS FERRIED WITH GEAR DOWN TO ZZZ1. IN ZZZ1 PROX SENSOR AND TARGET 256A WERE FOUND OUT OF LIMITS. REPAIRED AND RETURNED TO SVC. DUE TO THE FIXED NATURE OF THIS LINK ASSEMBLY; WE DID NOT RECHK THE RIG OF THE TARGET OR SENSOR. WE WERE UNABLE TO LOCATE A MAINT MANUAL FOR REMOVAL AND REPLACEMENT OF THE LINK. WE SHOULD HAVE INVESTIGATED THIS SENSOR MORE; DUE TO IT BEING THE ONLY PART DISTURBED DURING MAINT IN ZZZ.