The heater repairman returned on Monday. This time he had a new instrument in his toolbox, and, after a couple more hours of trial and error, got the warm air blowing again. It turned out to be an electrical problem.
Immediately after he left, I went to get something from my bedroom, switched on the light and got...nothing. I figured he had accidentally left a breaker switch turned off, so I went to the breaker box and found that the one labeled "master bedroom" was indeed switched off. Easy to fix, right? Well, no, it wasn't.
The repairman had removed the cover to the breaker panel, and when he screwed it back on, it slipped a little lower than it should have. Just low enough that it covered half of the master-bedroom breaker. And tight enough that I couldn't flip the breaker switch. My dining room and den lights were also affected.
He'd only been gone about five minutes when I called him to come back, but he was just pulling into another customer's driveway. Fortunately, that job turned out to be an easy one, and he was back here in less than an hour to set things right again.
The weather warmed up enough on Tuesday that I haven't used the heater since early that morning. Please cross your fingers for me that it works the next time I need it.