As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMBING THROUGH FL 280 HIGH PITCH SQUEAL STARTED ON FLT DECK DIVERTED TO PHL AND SQUEAL PERSISTED UNTIL BELOW FL 180 FACT 18JUL25 19:37 PHL PRESSURIZED AC IAW AMM 21-31-00 FOUND MAIN PAX DOOR TO BE LEAKING. CLEANED AND LUBED DOOR SEALS. OPS CHECK GOOD AC OK FOR SERVICE