Woke up late and wrapped in more blankets than usual, awakened by a Tam who was also in more layers than usual: the furnace seems to be no worky!
It may just be a wonky thermostat; it's an old-fashioned type, with actual physical contacts on a bimetallic element and it no longer goes "sproing" when adjusted back and forth past room ambient. On the other hand, the blower works; and with that, we're at the limit of what I'll do with a gas furnace when I can afford to hire an expert.
Called 'em, a local outfit I've used for years, and they're sending a tech out. 'til then -- brrr!
2 weeks ago