As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK, AUTO PRESSURIZATION INOPERATIVE ON CLIMBOUT. IN AUTO, BOTH VALVES INDICATED 90 PERCENT CLOSED AT FL 100. ATC REPORTS TRANSPONDER INOPERATIVE. CYCLED CB & GT, NO HELP. PERFORMED LANDING GEAR RETRACTION EXTENSION IAW MM. UNABLE TO DUPLICATE FAULT. MEASURED WIRING AT RELAYS R8686/ R8687. REPLACED R952 AND DP952. PERFORMED OPS TEST; IAW MM AND FOUND SATISFACTORY.