What was found
ON FLIGHT 4475 THE CREW REPORTED THAT DURING THE CLIMB THE PRESSURIZATION WAS INOPERABLE IN AUTO AND MANUAL MODES. THE CAPTAIN ELECTED TO RETURN TO DCA. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. INSTALLED NEW GROUND CONNECTION VALVE IAW AMM 21-22-04. NO DEFECTS NOTED.PERFORMED LEAK CHECK IAW AMM 21-31-00. NO LEAKS NOTED. FOUND AND REMOVED BROKEN VALVE FROM DUCTING. THE AIRCRAFT WAS RETURNED TO SERVICE.