As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF ROLL, CREW NOTED UNCOMMANDED HOT AIR COMING INTO CABIN AND FLUCTUATIONS IN CABIN PRESSURIZATION RATE. RETURNED TO BASE, LANDING WAS UNEVENTFUL. TROUBLESHOT AND FOUND EMERGENCY PRESSURE VALVE INTERMITTENT. REPLACED THE VALVE WITH AN OVERHAULED UNIT. OPS CHECKED GOOD.