I have an eight year old Pentair Mastertemp 400 that turns on and ignites for 5 seconds. It blows hot air from the exhaust when lit. It cycles 3 times, stops, then the red Service Heater light comes on. I have changed the control board, igniter control module, igniter, membrane pad (button pad), flue sensor, and voltage transformer with no luck. When the service heater light comes on, there are no error lights that light up in the control board or the igniter control module. Any help would be greatly appreciated.