What was found
NR 1 DUCT OVERTEMP MESSAGE APPEARED WHILE LEVELING AT FL400. CREW PERFORMED QRH AND AFTER SWITCHING TO ECS 2, NR 2 DUCT OVERTEMP MESSAGE APPEARED. HAD BOTH NR 1 AND 2 OVERTEMP MESSAGES ON SIMULTANEOUSLY. BOTH DUCT TEMPERATURES WERE VERIFIED OVER 200 DEGREES ON THE SYNOPTIC PAGE. POWER WAS AT IDLE ON BOTH ENGINES FOR THE DESCENT AND BOTH DUCT OVERHEAT MESSAGES DISAPPEARED ON FINAL AFTER ABOUT 10 MINUTES AT IDLE. PERFORMED OPS CHECK OF RAM AIR VALVE. FOUND RAM ACTUATOR WORKING BUT FLAP DISCONNECTED. REPLACED RAM AIR VALVE, OPS AND LEAKS CK GOOD. ALL WORK C/W IN REF TO AMM 21-23-03-710-810A, 21-23-03-000-801-A, AND 21-23-03-710-802-A, OFF PN: 505-18030-405, SN: 0000825096, ON PN: 505-18030-405, SN: 0000903541.