What was found
IN FLIGHT AT 10,000 FEET WE GOT THE AMBER CABIN DOOR OPEN AND THE CHECK DOORS CAS MESSAGES. WE RAN THE QRH AND RETURNED TO THE FIELD. CHECKING THE VENT DOOR SWITCH (S4) AND INSPECTING THE CABIN DOOR HANDLE FOR SECURITY. PERFORMED PROXIMITY SWITCH TEST AND ADJUSTMENT AS OUTLINED IN AMM 52-70·10. ADJUSTED THE SWITCH TO A GAP OF0.10 INCH.CABIN DOOR HANDLE. INSPECTED DOOR COMPONENTS FOR ABNORMALITIES. NO ABNORMALITIES WERE FOUND. / CONDUCTED AN OPERATIONAL CHECK OF THE CABIN DOOR, WHICH WAS SATISFACTORY AS PER AMM 52-10·00.