As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DEN - FLT 401 - AIR TURN BACK. FLIGHT CREW REPORTED AIRCRAFT WOULD NOT PRESSURIZE. MAINTENANCE PLACARDED THE RIGHT PACK HIGH FLOW MODE PER MEL 21-2-1. SUPPLEMENTAL INFORMATION WILL BE SUBMITTED WHEN IT IS AVAILABLE. THIS MRR IS A SUPPLEMENT TO CLOSE MRR NR F3LA-97-099. ON 4-6-97, MAINTENANCE REPLACED THE RIGHT FLOW CONTROL VALVE AND SYSTEM CHECKED OKAY. (X)