Six weeks of running heat in the greenhouse begins soon. Forecast for the weekend is lows into the teens. I may have to put the onion flats on the floor in there and cover them with a tarp. Other seedlings will have to be happy in the South Window for awhile.
I should have listened to
@flowerbug about firing up the furnace now and then during the "off-season" to blow out the spider webs. There are no guarantees for that little natural gas, garage heater, not after 20 years. I have had repair guys out through the years but the last one said that it should be replaced. It's failed a few times but quickly comes back online. I put an electric heater in there as backup and check the remote thermometer through the nights thru the last few seasons. Actually, the furnace performance has been exceptional in since that repair guy walked away with me guessing that it will cost well over $1000 to replace.
I tried to fire it up yesterday morning ... The control couldn't keep even the fan running by itself. After allowing it to struggle for about 30 minutes the fan decided it would work but not controlled by the thermostat. Late morning, I'd opened the vents a little and just left it on for about an hour. Tried again on automatic on the cooling cycle - it worked!
Still wouldn't kick on when the thermostat called for heat, this morning. I turned the fan on first then tried to get it to fire up. It did! ... But I don't want the fan to run continuously so that the heat can click on as needed. Still, I ran it like that for about an hour, burning out the spider webs. The greenhouse was at 60°f while it was 25° outdoors. Cycle on, cycle off ... soooo, switched fan to auto ... It worked!
By now, the sun was high, solar heating only allowed 2 cycles. We will see how it does tomorrow morning

.
Steve
C-3PO: Sir, the possibility of successfully navigating an asteroid field is approximately 3,720 to 1.
Han Solo: Never tell me the odds.