As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACFT WOULD NOT PRESSURIZE IN AUTO OR MANUAL. RETURNED TO FIELD. APPLIED HEAT FOR 10 MINUTES TO THE SEAL CONTROL VALVE. C/W GROUND PRESSURIZATION OF ACFT IAW AMM TASK 21-00-00-863-801. ACFT PRESSURIZED NORMALLY IAW AMM TASK 52-11-36-000-801. INSPECTED MAIN CABIN DOOR SEAL AND AFT CARGO DOOR SEAL. NO DEFECTS FOUND. RETURNED TO SERVICE.