Yesterday the thermostat went offline and completely dead except for tiny green light flashing above the word nest at a rate that appears random. House cold. I performed the following tests:
- Checked router status and sure enough nest is the sole device missing from client list.
- Checked power and wiring at furnace and found 27 VAC between Common ( Blue wire) and the Rc (Red wire) only. All other wires especially W, call for heat appeared open (~3 mV).
- Pulled non responsive nest and reproduced wiring voltage measurements at thermostat end, That is when I first noted flashing light.
- Replaced nest with iconic dumb Honeywell round thermostat. Bingo! Furnace fires up and heats house.
- Checked clock at 12:15 PM and went to bed.
So what now. Do I pronounce it and replace with another brand?
