It’s been warm for the past few weeks in SoCal, and I turned the thermostat off a while ago. But there’s a weather system coming in this weekend that’s going to cool things down, and it was chilly in the house this morning. I turned the thermostat back on, and nothing happened. I checked the fuse, and it’s fine, the switch seems to be on. I’ve determined that there is no power getting to the power switch (which feeds the fuse, which feeds the furnace electronics). No breakers are tripped, and I don’t know which breaker it’s on. Any ideas? If it’s actually failed wiring, that could be nightmare to trace/repair.

[Saturday-afternoon update]

Welp, checked all the breakers, and they all have voltage at the output.

[Sunday-morning update]

Thanks for all the advice in comments. I suspect I’m going to have to kill power to the house, and try to do an RF trace (and hope it comes through the armor). Fortunately, it’s not really an emergency. The temp in the house was 64F when we woke up this morning, and while it will be a cool couple of days until this cutoff low with rain passes through, it will be heating up later this week. Worst case is sweaters and a heavier bed covering, until I figure it out.