As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IR: 20KFT CABIN ALTITUDE HORN WENT OFF.CBN ALT AT 11 KFT. STARTED DESCENT SWITCHED TO STBY CBN WOULD NOT PRESS. MANUAL MODE ALSO INOP. REPLACED E & E COOLING EXHAUST VALVE. ALSO FOUND LEFT ENGINE 450 DEG THERMOSTAT SENSE LINE BACKED OFF. TIGHTENED SAME,RAN ENGINES ACFT PRESSURIZED TO 5 PSID.