As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 710 MID-MIA, DURING CLIMBOUT CREW REPORTED PRESSURIZATION OUTFLOW VALVE WOULD NOT CLOSE IN ANY MODE IN FLIGHT ON DEPARTURE FROM MID. AIRCRAFT RETURNED BACK TO MID WITH NO FURTHER INCIDENT. MAINTENANCE ACCOMPLISHED A PRESSURIZATION CONTROL SYSTEM TEST IAW BOEING 727 MM CH-21-31-0 & AMERIJET PRESSURIZATION CHECK WORK CARDS 7-29. OUTFLOW VALVE OPERATION CHECKOUT NORMAL. AIRCRAFT RETURNED TO SERVICE.