What was found
ON CLIMB OUT, ENROUTE, CREW REPORTED THE LEFT MAIN LANDING GEAR WOULD NOT RETRACT AFTER PLACING GEAR LEVER TO THE UP POSITION. THE LEFT MAIN LANDING GEAR UNSAFE LIGHT WAS ALSO ILLUMINATED. CREW RECEIVED NORMAL GEAR INDICATION OF THREE GREEN LIGHTS WHEN GEAR WAS EXTENDED. FLIGHT RETURNED AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE LEFT MAIN LANDING GEAR RETRACT ACTUATOR PER MM. ALSO, REMOVED AND REPLACED LEFT MAIN LANDING GEAR UPLOCK SENSOR (PN 189929). OPERATIONAL CHECK AND LEAK CHECK GOOD.