Furnace ignites, goes out, ignites, out

[Ricker]

Pulled furnace. Seen no water problem. Circuit board had no corrosion. Checked for loose connections. Getting set up to bench test the furnace. Will respond back after I do some bench testing. I think it’s not sensing the flame when furnace ignites. Shuts down in about 1.5 seconds. Ignites briefly. Ignites again in about 15 seconds. This sequence continues (guess this is a soft reset). Never shuts down completely (hard reset). Not sure what senses flame. All I can see is one wire going to the ignitor.

[JFlightRisk]

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[Parrott]

Originally Posted by Ricker

Pulled furnace. Seen no water problem. Circuit board had no corrosion. Checked for loose connections. Getting set up to bench test the furnace. Will respond back after I do some bench testing. I think it’s not sensing the flame when furnace ignites. Shuts down in about 1.5 seconds. Ignites briefly. Ignites again in about 15 seconds. This sequence continues (guess this is a soft reset). Never shuts down completely (hard reset). Not sure what senses flame. All I can see is one wire going to the ignitor.

I believe the igniter senses flame too. Possible bad board. Check all your board connections and look for cold solder joints. I had the same symptoms and replaced my board. I looked carefully at the old board with a magnifying glass and found a bad solder joint. Resoldered and the board works. I now have a spare. I bought the dinosaur board.

[Ricker]

After I pulled furnace I reseated all the electrical connections. I also noticed when I pulled the furnace it only had one bracket holding it in place. I think the furnace had shifted. I don’t think the exhaust was lining up with the exhaust vent correctly causing some back pressure on furnace which was causing it to shutdowm quickly after ignition. I bench tested the furnace outside the camper with the exhaust vent placed in the exhaust. Worked great. Reinstalled and added another brace. Unit worked. My furnace did not have an access door. Had to access through the front storage area. Was not easy to pull. So, either reseating the electrical connections or the exhaust was not lined up correctly with the vent. I think it was the exhaust vent out of alignment. Thanks to for all the helpful comments.

[jetlag]

Great news, glad it's fixed.

[JakeofAllTrades]

Checked sail switch, high limit switch, electro-magnets on gas valve, cleaned outside exhaust tube, cleaned flame sensor ignition electrode, checked for spark on ignition electrode, full propane tank, then tested water column pressure on propane tank regulator. The pressure was 12.5 inches of water and specs call for 11 inches of water. Adjusted regulator to 11 inches, reassembled all parts, and the furnace worked perfectly. High gas pressure may have caused the flame to "blow out."