What was found
IAH - FLIGHT 2962, THE CREW REPORTED A BLEED 1 CLOSED EICAS MESSAGE FOLLOWED BY PACK 1 CLOSED EICAS MESSAGE APPEARING REPEATEDLY, THE APU WAS USED FOR PRESSURIZATION, AND A CABIN HIGH ALT WARNING WAS RECEIVED. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE AIRCRAFT AND REMOVED AND REPLACED A SLEEVE ON THE NUMBER ONE ACM, OPERATIONALLY TESTED WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.