What was found
AFTER TAKE OFF, RECEIVED AN AMBER GEAR LIGHT AND A GEAR DISAGREE MESSAGE ON EICAS. RAN CHECKLIST, PROBLEM DID NOT RESOLVE ITSELF. PUT GEAR DOWN AND RECEIVED A NORMAL THREE GREEN INDICATION. RETURNED TO DEPARTURE. THE NOSE LANDING GEAR LOCK ACTUATOR REMOVED AND REPLACED. PROXIMITY SWITCH ELECTRONICS UNIT (PSEU) REMOVED AND REPLACED. SYSTEMS OPS CHECKED GOOD IAW AMM 32-32-00-5. RETURNED VMO/MMO SWITCH TO NORMAL IAW AMM 34-12-00-5. REMOVED LANDING GEAR LOCKPINS IAW AMM 32-00-20-2. REMOVED COLLAR AND RESET LANDING GEAR LOCK LEVER CIRCUIT BREAKER IAW AMM 20-60-01-2.