As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - FLIGHT 2316 - THE FLIGHT RETURNED TO FIELD, UNABLE TO GET HEAT FROM EITHER THE CABIN OR COCKPIT PACKS. MAINTENANCE INSPECTED THE AIRCRAFT AND REPLACED THE PACK FLOW CONTROL AND SHUTOFF VALVE FILTER. OPERATIONAL CHECKS WERE GOOD AND THE AIRCRAFT WAS RETURNED TO SERVICE.