Thermostat Not Working

When this becomes an emergency

• The screen is dark, or it lights up and then drops out again.
• The temperature it reports is several degrees off from what the room actually feels like.
• Raising the setpoint produces no reaction from the equipment at all.
• The schedule wipes itself and reverts to defaults on its own.

What a pro does

Batteries and a loose wire cover most of these. A technician checks for twenty-four volts at the thermostat terminals, then jumps the heat call at the equipment to see whether the furnace or boiler responds, which separates a control fault from an equipment fault in about a minute. If the equipment fires on a jumper, the problem is upstream. Older houses complicate this because thermostat wire gets spliced and rerouted during remodels, and a corroded connection buried behind a wall plate reads as a dead thermostat. Smart thermostats add the common-wire question, since a unit power-stealing through the heat circuit will brown out and reset instead of holding steady. Placement explains most of the wrong-reading complaints we hear about, and it's the cheapest thing on the list to correct. A thermostat mounted on an exterior wall of a stone farmhouse reads that cold wall, not the room, and it will run the system too long every single cycle.

Frequently asked questions

Thermostat Not Working?

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