Help - intermittent combustion heater

[Bob Cook]

Does the orange light come on (over temp) when the heater shuts down ?

If it overtemps then it must be combustion air (not enough). The thermosat should cycle the heater. If you run the thermostat all the way down does the heater cycle at all ?

Perhaps you are looking at a wiring problem and not the heater. A chaffed wire ?

90% of the time they just don't fire. This one is really strange since you have replaced the heater in its entirety.