What was found
IAH- FLIGHT 3959,THE CREW NOTED THAT THE AIRCRAFT HAS A LIGHT TO MODERATE VIBRATION IN CLIMB (290 KIAS) THROUGH CRUISE (320KIAS). FELT IN FLOORBOARD, AND, SEAT IN COCKPIT. NO VIBRATION NOTED ON YOKE. IAH- MAINTENANCE INSPECTED THE FORWARD INLET AIRFLOW SHUTOFF VALVE,AND, FOUND THE VALVE TO BE INTERMITTENT. REMOVED AND REPLACED RELAY K0039 FOR SHUTOFF VALVE TEMP CONTROL. PERFORMED A OPERATIONAL CHECK, NO DEFECTS NOTED, AND, THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.