As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TEMPERATURE CONTROL VALVE DIAPHRAGM RUPTURED CAUSING DAMAGE TO DIAPHRAGM BODY AND SEVERING ACTUATING LINKAGE. AIRCRAFT WAS PREPARING FOR DEPARTURE WITH NO CONTROL OF COCKPIT HEAT. HEAT WAS FULL HOT. VALVE WAS REPLACED AND A CONTROL PRESSURE CHECK WAS C/W. INDICATIONS AND OPERATION WERE NORMAL.