What was found
A GEAR DISAGREE LIGHT ILLUMINATED AFTER GEAR RETRACTION LEAVING EWR. ALTERNATE GEAR EXTENSION WAS PERFORMED AND THREE GREEN WERE INDICATED. THE AIRCRAFT WAS RETURNED TO EWR WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE L/H MLG DOOR LOCK RELEASE ACTUATOR AT FAULT. THE LOCK RELEASE ACTUATOR WAS REMOVED AND REPLACED IAW MM 32-35-06. A GEAR SWING WAS PERFORMED AND OPERATION CHECKED GOOD.