What was found
UPON TAKEOFF AND GEAR RETRACTION, OBSERVED NOSE GEAR UNSAFE LIGHT. RECYCLED AND THE SAME INDICATION WAS OBSERVED. DURING PERFORMANCE OF THE ABNORMAL CHECKLIST THE CREW REPORTED THE ILLUMINATION OF THE LEFT MAIN GEAR UNSAFE LIGHT. RETURNED AND LANDED UNDER NORMAL CONDITIONS WITH NORMAL DOWN AND LOCKED INDICATIONS. INSPECTED THE LANDING GEAR, A GEAR SWING WAS PERFORMED AND THE ILLUMINATION OF THE NOSE GEAR UNSAFE LIGHT WAS CONFIRMED. NO ABNORMAL INDICATIONS OF THE LEFT MAN GEAR WERE OBSERVED. TROUBLESHOT USING THE DC9 MM 32-60-0, 32-60-1 AND WIRING DIAGRAM 32-61-00. THE PROBLEM WAS ISOLATED TO THE NOSE GEAR OVER CENTER LINK PROXIMITY SENSOR. THE SENSOR WAS RELACED IAW DC9 MM 32-60-1 AND THE LEFT GEAR SENS