[Twopetes]

Just wanted to add something that we had happen and just something to keep in your pocket. Our furnace acted similar. It turned out that the main LP regulator was bad and it was not allowing enough gas pressure when we lit the furnace. If there was a few minutes of nothing running before the thermostat called for the furnace, the gas pressure would build up enough for the furnace to fire, but there would not be enough pressure and flow to keep it running. Our local repair shop took a couple days but they found it. Regulators don’t last forever. I had to replace the regulator on the other LP tank and both pig-tails on our 15 HC. Always check for leaks! Good Luck!