What was found
IAH - FLIGHT 2547, DURING CRUISE THE CREW REPORTED THAT PRESSURIZATION WAS INOP IN AUTO, AND COULD NOT BE CONTROLLED IN MANUAL. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE PRESSURIZATION CONTROLLER, OPERATIONALLY TESTED WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.