What was found
A/C RETURNED, DUE TO "UNSAFE NLG" LIGHT TURNED ON & STRONG NOISE DETECTED. A/C SENT TO HANGAR & NOSE L/G DOORS INSPECT, DOORS TEST & EXTENSION/RETRACTION TEST WERE PERFORMED IAW MM 32-20-00, 32-22-01, 32-30-00, RESPECTIVELY, ALL CORRECT. DURING CLIMB IN NEXT FLT, A/C RETURNED OF FLT BY SAME FAILURE & A/C SENT TO HANGAR AGAIN. DURING OVERNIGHT SERVICE, NLG STRUT SERVICED, NLG DOORS PRECHARGE CHECKED, GEAR UP & LOCKED SENSOR & NLG ACTUATOR REPLACED, EXTENSION/RETRACTION TEST PERFORMED IAW MM 32-21-02, 32-22-01, 32-60-05, 32-32-06 AND 32-30-00, RESPECTIVELY. SENSORS D1-31 AND D1-32 WERE CHECKED & SENSOR D1-31 WAS REPLACED IAW MM 32-60-00, ALL CORRECT. O/W INSPECT PERFORMED IAW MM 05-51-04 AND TEST FLT WAS PERFO