I've power cycled the unit several times during my testing. At times the fan will come on and the burner will come on and seem to be working fine, then will cut off before water reaches temp.
Some times the fan will come on and before the burner can come on the fan will cut off. Some times the fan will repeatedly try and cycle, come on, but will cut off in just a few seconds.
The led usually fast flashing-calling for heat. Several times the led has flashed 4flashes-lockout condition, switch fails to close.
At least one time the led flashed 3flashes-lockout condition,switch fails to open.
I've taken the fan off the water heater and it seems to be fine, while I had the fan off, I checked the vent pipe running a fish tape from the heater to the out side of the house. There wasn't any visiable or physical obstruction in the vent pipe.
How do I test the pressure switch and thermal switch?
Perhaps you have experience with trouble-shooting and testing electronic devices, but since you have asked the question, I suspect you do not. I don't wish to offend you, but there are times when even manly men have to ask for help. I suggest that this may be one of those times.