What was found
AFTER TAKEOFF, THE LEFT MAIN GEAR DOOR CAUTION LIGHT ILLUMINATED AND THE GEAR DOOR WAS CONFIRMED TO BE IN THE OPEN POSITION. WHEN THE GEAR WAS CYCLED DOWN, ALL INDICATIONS WERE GREEN. THE CREW THEN CYCLED THE LANDING GEAR UP AND GOT THE SAME CAUTION INDICATION. THE CREW THEN ELECTED TO RETURN TO THE FIELD, BUT DID NOT DECLARE AN EMERGENCY. EMERGENCY EQUIPMENT WAS DISPATCHED BY THE TOWER AND FOLLOWED THE AIRCRAFT AFTER A NORMAL LANDING. MAINTENANCE CHANGED THE FORWARD GEAR DOOR ACTUATOR AND CHECKED RIGGING OF THE ACTUATOR AND DOOR SENSOR. OPS CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.