This has happened twice now and both times it exclusively involved the onboard propane tank and only occurred in we morning hours.
Background: Until yesterday, I was using an extend-a-stay with a 20lb tank as my primary, saving the 40lb onboard to run the fridge while traveling and as a backup should the 20lb'er go dry without warning. I have to replace the float and gauge in the onboard tank and no one can retrieve the propane and put it back (or they don't want to). I am where I am for a month so I figured I'd run the tank dry and have it fixed so the control panel lights would be correct again.
The first time it acted up using the onboard tank was back in early December, before I got the extend-a-stay. In the middle of the night, the heater starts clicking (ignition?). The fan won’t spin and the heater won't ignite. The first time, I pulled the fuse, let it sit a minute and plugged it back in. All was fine.
Last night - in the middle of the night, it acts up again. I pull the fuse like last time only this time, no dice. The fan would run but the furnace wouldn't ignite. I turn on the stovetop thinking maybe the tank was dry, thinking it wasn’t really possible because I only used the onboard for traveling. I let it burn for a while just to make sure it wasn’t left in the line(s).
I pulled the thermostat back to turn it off. The thermostat clicked (no call for heat) and the fan starts oscillating. Run the thermostat up, fan runs normal, no ignition - pull it back and it oscillates.
I go outside, close the external tank, open the external tank and the furnace lit right up and ran all night. Went out this morning swapped them back out and the heater has been running all day without a problem.
The most bothersome is it’s not consistent. The second is it only happened in the middle of the night.
Has this ever happened to anyone else and, if so, what was the final verdict?
Thanks in advance for any feedback you offer.