What should I do if my furnace will not turn on?

What this symptom usually means

When a furnace will not turn on at all, the key question is whether the unit has lost power or whether it is receiving power but refusing to start its sequence. A furnace that is completely silent and has no display is usually dealing with a power or control-voltage problem. A furnace that clicks, hums, flashes a code, or starts for a few seconds and stops is usually failing at a specific step in the ignition sequence rather than simply "not heating."

How to tell the likely causes apart

If the thermostat is calling for heat and the furnace has no lights, no sound, and no display, look first for a tripped breaker, a furnace switch that looks like a light switch near the unit, or an access panel that is not fully seated on the cabinet. If the breaker is tripped again immediately after reset, stop there and schedule service, because that points to an electrical fault. If the furnace display is on but the unit does nothing, a thermostat signal problem, low-voltage fuse, or open safety circuit becomes more likely.

If you hear a click, hum, or brief startup attempt, that tells a different story than a dead-silent furnace. Many furnaces begin with the inducer motor, then prove airflow through a pressure switch, then energize the igniter, then open the gas valve, and finally bring on the blower. A code or repeated failed attempts often means the control board knows where the sequence stopped, which helps narrow the repair to the igniter, inducer, pressure switch tubing, condensate issue, flame proving circuit, or board.

What a service visit usually includes

A technician will usually verify line voltage to the furnace, check the breaker and service switch circuit, confirm the door switch is being pressed, and test whether the thermostat is actually sending a heat call on the low-voltage terminals. From there, they will read any fault codes, inspect the control board and fuse, and follow the startup sequence step by step to see where the furnace stops. On condensing furnaces, they may also check condensate drainage and pressure-switch operation because a backed-up drain can lock the unit out before ignition.

What affects repair cost

Cost depends heavily on whether the problem is external power, a minor control issue, or a failed furnace component. Typical 2025-2026 U.S. repair ranges are roughly $170-$575 for a basic electrical or thermostat-related fix, about $170-$575 for igniter, pressure-switch, or inducer-related diagnosis and repair, and around $500-$1,575+ if the control board or inducer assembly has failed. The final number also changes with furnace type, part availability, after-hours timing, and whether repeated lockouts caused additional diagnostic time.