Thermostat not working? Check these first.
A thermostat that is blank or unresponsive is often a simple power problem — and sometimes the thermostat is fine and the system behind it is the real fault.
Start with power.
The large majority of "dead thermostat" calls come down to batteries, a tripped breaker, or a safety switch elsewhere in the system cutting power to the thermostat.
- The screen is blank or the display is dim and flickering.
- It responds but nothing happens — no heating or cooling starts.
- The room temperature reading looks wrong compared to how it feels.
- It works intermittently or resets itself.
What to check, in order.
1. Batteries, even on a wired thermostat. Many thermostats that are wired to the system still use batteries for the display and memory. A blank or faint screen is very often nothing more than this. Replace them with fresh ones rather than testing with used spares.
2. The breaker and the system power switch. If the thermostat draws its power from the heating or cooling system, anything that cuts power to that system also kills the thermostat. Check the breaker panel, and check the switch on or beside the furnace or air handler — it looks like an ordinary light switch and gets flipped off accidentally.
3. The furnace door panel. There is a safety interlock behind the front panel that cuts power when the door is not seated. If someone changed a filter recently and did not click the panel back firmly, the thermostat can go dead. This catches people out constantly.
4. A tripped float switch from a blocked drain. On systems with a condensate drain, a blocked line fills the pan and a float switch cuts power deliberately — which can take the thermostat with it. If there is water near the indoor unit, that is your answer, and clearing the drain restores everything.
5. Settings that look like faults. Confirm the mode is on HEAT or COOL rather than OFF, and that the target is set far enough from the current reading to trigger a cycle. Check whether a schedule or a hold is overriding you — a programmed setback is a very common "my thermostat is broken" that is really working as configured.
6. Placement, if the reading seems wrong. A thermostat in direct sun, above a register, beside a lamp or on an exterior wall reads a temperature the rest of the house does not share. That causes short cycling and rooms that never feel right. The thermostat is accurate; it is measuring the wrong spot.
7. When it is not the thermostat at all. If the display is fine and the settings are right but nothing happens, the fault is usually downstream — a failed igniter, a tripped safety, a dead capacitor or a wiring break between the thermostat and the equipment. Replacing a working thermostat will not fix any of those, which is why it is worth confirming the above before buying a new one. If the thermostat is set correctly and the furnace still refuses to fire, work through our furnace not turning on guide in order — most of those checks take under a minute and need no tools.
When the dead thermostat means no heat and you cannot wait. If an unresponsive thermostat has left the house with no heat in freezing weather — especially overnight or with young children, elderly, or unwell people in the house — that is not a morning-appointment situation. The 24/7 emergency HVAC dispatch covers exactly this: round-the-clock response for no-heat situations that cannot wait. That after-hours coverage runs across Spokane and the nearby towns, and the Spokane County service areas page notes what changes town by town.
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Questions homeowners ask.
Why is my thermostat screen blank?+
Most often dead batteries, or a loss of power to the system it is wired to — a tripped breaker, the furnace power switch turned off, a furnace door panel not clicked shut, or a float switch tripped by a blocked condensate drain.
My thermostat works but nothing turns on. What now?+
That usually points downstream of the thermostat: a tripped safety, a failed igniter or capacitor, or a wiring fault between the thermostat and the equipment. A new thermostat will not resolve any of those. If it is the cooling side specifically — the thermostat is set to cool and nothing starts — our Spokane AC repair page covers the outdoor unit faults (failed capacitor, tripped outdoor breaker, bad contactor) that most often look like thermostat problems from inside.
Does thermostat placement really matter?+
Yes. Direct sunlight, a nearby lamp, an exterior wall or a spot above a heat register all make it read a temperature unlike the rest of the house, which causes short cycling and uneven comfort even though the thermostat itself is accurate.
My thermostat calls for heat but the vents blow cold — what now?+
That is a different symptom from a dead thermostat and points at the furnace side. The single most common cause is a dirty flame sensor that shuts the gas off within seconds of ignition and leaves the blower pushing cool air; a clogged filter overheating the unit is a close second. See our furnace blowing cold air guide for the full list and how to tell them apart.
My thermostat keeps showing "aux heat" or "em heat" — is that a fault?+
It is not a fault of the thermostat itself; it is the thermostat honestly reporting that a heat pump has fallen back to its electric backup. In genuinely cold weather that is designed operation and clears when temperatures rise. If it happens in mild weather, or stays on for days, the heat pump is underperforming — low charge, a stuck defrost cycle or a failing outdoor fan — and the resistance backup runs up the power bill in the meantime. See our heat pump repair page for what to check and when to book.
My thermostat is fine but my furnace is old — is the next repair still worth it?+
A thorough thermostat check often reveals the real problem: an aging furnace where the next repair bill no longer makes sense against the years remaining. The rule of thumb is to multiply the repair quote by the furnace's age in years — if that number comfortably exceeds the cost of a new system, replacement usually wins. See what a replacement furnace costs in Spokane for honest price ranges to run the comparison; if replacement is the right call, the furnace installation page explains what a proper install involves and what to get in writing before work begins.
Can I get this looked at in the Spokane area?+
Yes — answer a few quick questions and your details go to a local HVAC company serving the Spokane area, who will give you a price before any work begins. Ask them for their license number and check it free at Washington L&I; we pass on the job, we don’t vet the paperwork.
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