My h100idp1 will turn on, fire, stay on for 10 seconds, then the burner goes off but the fan keeps running. It stayed on once for about 15 minutes then shut off again. Now it will not stay firing. Worked for 2 years ok until now.
Just had the same experience.
1. Pull the top cover off and try gently wiggling the printed circuit board on the right side top. Pull the thermostat mounting board too if it helps. Be careful as it is still live as you are doing this. If it fires, unplug it & remove the board from the unit. Get a magnifying glass and a good light and go over the solder connections on the back of the board, ALL of my connections where the harness plugs into the board were cracked. Best as I can figure, the board is mounted right next to the power vented flue discharge and it is extremely hot there and must expand & contract with heat especially if wind is blowing the heat back onto the unit. Re-solder connections & mount the board somewhere else in the unit.
2. The igniter assembly acts as a thermocouple, which is to say it "proves" the flame to the unit telling the gas valve to stay open and the spark to shut off as long as the thermostat wants the unit to run. That component may have failed & requires replacement.
3. The flow switch (Pressure sensor) proves water flow to the unit saying it is ok to fire. I've replaced mine twice due to them busting open, but that can also hold out the unit if it doesn't sense flow,however but I doubt that is the culprit. It is easy to test, just make sure the pump is on, jump the wires & turn on the unit. MAKE SURE to put them back on after testing as the water will boil very rapidly if the unit runs with no flow which is extremely dangerous.
I would check these components in that order.
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