A thermostat click means it is sending the signal, so the problem is usually the equipment: a compressor delay, no power at the furnace, a tripped float switch or a loose wire.
If your ecobee is not heating, check for Calibrating, the mode and setpoint, power and the C wire, wiring, and the equipment settings in the ecobee. When it says it is heating but the house stays cold, the problem is usually the furnace or heat pump.
If your Nest keeps showing AUX and your bills are climbing, Heat Pump Balance is the setting to change. What Max Comfort, Balanced and Max Savings do, how to change them and other reasons aux heat runs too much.
If the thermostat says it is heating but the house stays cold, the signal is not reaching the furnace, the furnace will not light, or the heat is not reaching you. Nine checks in order.
“Recovery” on a Honeywell thermostat means it started heating or cooling early to reach your next scheduled temperature on time. How it works, when it signals a problem, and how to turn it off.
Most Nest thermostats charge from your HVAC wires, so a low battery usually means a power problem. How to charge it, find the cause and fix it for good with a C wire or adapter.
A flashing “Cool On” usually means the compressor protection delay is running and the AC will start within about 5 minutes. When it lasts longer, here are 8 fixes to try in order.
Honeywell thermostat not working? Fix blank screens, flashing Cool On or Heat On, wrong readings and heat pump settings with this step-by-step guide.
What does Delayed mean on a Nest thermostat? Learn the difference between normal compressor delays and low-power delays, and how a C wire fixes it.
Ecobee or Nest? Compare price, room sensors, smart home support, heat pump controls, C-wire needs and energy savings to pick the right smart thermostat.