Furnace Issues

[NG7V]

I have a Thor Aria 3910/2019. Since last winter, I have had propane appliance problems. My recollection is that problems began after my last fill at a campground in Yuma.

My on-demand water heater intermittently failed with no flame errors was the first indication, second, I started noticing that my furnace was limiting. After a 3-5 minute burn, it would turn off the burner, keep pushing air and turned the burner on again. I attributed that to a possible overheating condition after a long burn. I paid no mind to all this until this last summer.

The on-demand water heater condition got worst. After a trip to Jordan Valley OR, I decided to replace the propane regulator. There was an immediate improvement with the water heater but not the furnace. In fact the furnace got worst. I would fire up the burner twice to stay lit and it was still limiting. It got to fail so bad that it went into a lock state when it got really cold. So, I got working on the furnace thinking that the gas pressure was good.

I noticed that the furnace misbehaved at external temperatures below 48F. but never failed at warmer temps. Not an ideal condition but at least I could make it fail by getting up early in the morning and testing it.

I replaced the circuit board thinking that the only temp sensitive component in that furnace was the electronic part of it. The situation improved but still not perfect. It only did a single retry to light up but it was good enough to maintain the interior temperature to the thermostat setting.

Next, I took out the burner, cleaned out the electrode and the hydro-flame burner with steel wool to get rid of any stain or coating on any surface. Put everything back together. It failed again the next day.

I disconnected and bypassed the temp limiting sensor with a jumper and it failed again the next morning.

I ordered a new flame sensor and while waiting for the delivery, I did more research and came across a YouTube video of an elderly man who was fixing a grill that was not coming up to temperature beyond 350 degrees. He explained that by releasing some propane through the bleeder valve for a few minutes would purge his cylinder of the air that it contained. The result was that after the bleed, his grill temp went up to 450 as it should.

I got the idea to bleeding my tank for a few minutes to see if it would make a difference. I did and guess what, my furnace problem seems to have gone away.

I will replace the flame sensor when I get it, just to be sure.

My theory is this:
Whatever I bled out of that tank is what was mixed in with the propane going to my furnace. The inclusion of whatever it was caused the temperature of the flame to go down. The difference was enough to trip the flame sensor on the first try but always recovered on the second try as the burner warmed up. I think that if the temps would have dropped into the teens, the furnace would have completely failed.

I had 3 problems: The board sensed the flame sensor in a positive tolerance, the flame sensor sensed the temperature of the flame in the opposite direction and I had some sort of mixture issue in my propane tank.

I could not see the flame and I have no way of seeing if it is blue or not, I did not have a gas stove to look at it because mine is electric. So I had no way of knowing if I had a pressure problem. I did not have a manometer to measure anything and I don't think I would have seen a pressure issue (new regulator)

My question to Y'all is: What was in my tank that the last fill added? Air? Butane? Combination of things? How did it get in there?

The warning: if your appliances get to be flaky and you have more than one failure, look in the direction of the propane you last purchased and bleed your tank (carefully because this s**t goes boom if you are not careful).