What was found
BOS - FLT 1116 - ON CLIMB-OUT FROM BOS, EN ROUTE PHL AT 6,000 FEET, THE CABIN RATE OF CLIMB WAS FLUCTUATING FROM 3,000 FEET PER MINUTE TO 2,000 FEET PER MINUTE IN AUTO MODE. MANUAL MODE WAS INOPERATIVE. AIRCRAFT FAILED TO PRESSURIZE, SO THE FLIGHT RETURNED TO FIELD AT BOS AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE CABIN PRESSURE CONTROLLER. OPS CHECK PER MM 21-31-00. ALL SYSTEMS CHECK NORMAL. MANUAL MODE CHECKED NORMAL ON THE GROUND. (M)