What was found
AIRCRAFT WAS GROUNDED: CABIN PRESSURIZATION FAULT CABIN NOT PRESSURIZING AT 14,000 FT DESCENDED TO 10,000 FT. ALSO ENCOUNTERED A VENT BLOWER FAULT AND EXTRACT FAULT AT 12, 000 FT. EXTRACT VALVE OPEN ENTIRE TIME. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO ORD WHERE IT LANDED SAFELY WITHOUT FURTHER INCIDENT. MAINTENANCE PERFORMED TSM 21-60-00 AND VERIFIED THE SKIN AIR OUTLET VALVE 22HQ WOULD FAIL INTERMITTENTLY AND REPLACED IT PER AMM 21-26-53. A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED OF THE AIRCRAFT PRESSURIZATION SYSTEM WITH NO DEFECTS NOTED.