Dang thing won't stay heating. Sometimes will respond perfectly to set-back thermostat for weeks.
Then has to be hit in the area of insignia, area of the draft inducer, before flame will start and fan start. The hitting involves significant trek outside, cold outside and inside. This has been going on for a couple of weeks now, will run for 15 min. or 2 hours, but goes back off before keeping house to right heat.
Uses an LPG conversion kit.
Am plenty irritated, installers out of business. Furnace is v. low energy efficiency, only about 5 years old.
Have reasonably priced service-man to call, but would like him to have best information.

I suggest calling in your serviceman. If he is a good serviceman, he won't need any information from you. All you need to say is, this thing just don't work right. And he should be able to take it from there. If its an intermittant problem, it can be very hard to trouble shoot, even for a pro. I suggest having the service tech come when the unit is failing, if at all possible. Good luck and please let us know what he finds.