What was found
AIRCRAFT WAS GROUNDED: CLIMBING THROUGH FLIGHT LEVEL 200 FELT A PRESSURE BUMP THEN ELECTRONIC CENTRALIZED AIRCRAFT MONITOR CAME UP SHOWING THE CABIN CLIMBING AT 4100 FEET PER MINUTE. FINALLY SETTLED DOWN TO A 600 FEET PER MINUTE CLIMB - CABIN MADE IT TO 9200 FEET - RETURNED TO FIELD. FLIGHT WAS NOT OVERWEIGHT FOR LANDING. FOUND NUMBER 2 PACK OUTLET BELLOW CRACKED AND BLOWN OUT AT CONDENSER INSTALLED SERVICEABLE CONDENSER AND REPLACED NUMBER 2 PACK OUTLET (AALA202112139193) BELLOW.