What was found
HLN ON FLIGHT 2323- AT FLIGHT LEVEL 250, ENCOUNTERED MODERATE TURBULANCE FROM MOUNTIAN WAVE ACTIVITY. FUSELAGE DOORS WARNING LIGHT ILLUMINATED AND SYSTEMS PAGE SHOWED A RED AFT PASSENGER SERVICE DOOR ON CAPTIAN'S SIDE. COMPLETED EMERGENCY CHECKLIST AND FLIGHT ATTENDANT REPORTED DOOR WAS CLOSED AND HANDLE WAS IN CLOSED POSITION. NO ABNORMAL SOUNDS, LIGHT WENT OUT AFTER LANDING. CLEANED ICE/WATER/DEBRIS FROM PROXIMITY SENSOR. NO PARTS REPLACED. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.