What was found
PILOT REPORTED SMELL OF EXHAUST IN CABIN AND CO DETECTOR STARTED TO CHANGE COLOR WHEN RUNNING CABIN HEATER IN CLIMB. A PRESSURE DECAY TEST REVEALED A BREACHED COMBUSTION LINER IN THE CABIN HEATER (865.6 HOURS SINCE NEW). THE CABIN HEATER WAS REPLACED WITH NEW. THIS IS THE 2ND CONSECUTIVE HEATER BY THIS MANUFACTURER THAT HAS EXPERIENCED A SIMILAR FAILURE AT LESS THAN 1000 HOURS SINCE NEW. THE ROUTINELY SCHEDULED PRESSURE DECAY TESTS DO NOT START UNTIL 1000 HOURS SINCE NEW.