Furnace won't turn on?

If there's no fan, no click and no light, it's usually a tripped breaker, the power switch, a thermostat issue, or a door switch. Check those before assuming the furnace has failed.

Not sure which one it is? Snap your furnace and we’ll narrow it down.

Does the fan run but the air stays cold?

That's a heating problem rather than a power problem. Furnace won't heat

Likely causes

  1. Tripped breaker or furnace power switch off

    Most commonEasy DIY

    No lights, no fan and no display on the furnace; the breaker is in the middle or off position, or the wall-style switch near the unit was bumped.

  2. Thermostat problem

    Most commonEasy DIY

    Blank screen, dead batteries, or set to Off or Cool. The furnace does nothing because it's never asked to run.

    Part: $5–15 (batteries)

  3. Blower door or panel not seated

    CommonEasy DIY

    The furnace has power but won't start; the door panel was recently removed, such as after a filter change, and a safety switch isn't pressed.

  4. Clogged condensate drain or full pan (high-efficiency furnaces)

    CommonModerate DIY

    Water near the furnace or a drain line that's backed up, with the unit shutting off on a float switch.

  5. Failed control board, transformer or blower motor

    Less commonCall a pro

    Power reaches the unit but nothing responds, a status light flashes a fault code, or a burning smell.

    Part: $200–2,000

Quick checks

If you smell gas (rotten eggs), or a carbon monoxide alarm sounds, leave the house immediately and call your gas utility or 911 from outside; don't touch switches. Reset a breaker once only. If it trips again, stop and call an electrician or HVAC pro, because repeat tripping means a fault. Don't open the burner area, touch the gas valve, or work on wiring.

  1. Confirm the thermostat is on Heat, set above room temperature, with fresh batteries.
  2. Check the furnace power switch and the breaker in the panel; reset a tripped breaker once only.
  3. Make sure the blower door or front panel is fully seated, since the furnace won't start if it isn't.
  4. Look for a status light through the small window and note any flashing pattern.
  5. Check that the filter isn't severely clogged.
Sharpen the read

Diagnose your furnace in seconds, for free

No account, no phone number. Fixology’s AI reads your photo and tells you what’s likely wrong, how worried to be, and whether it’s a DIY fix.

Snap one of these:

  • the status light through the small window on the lower door, and its blink pattern
  • the model label on the side of the unit
  • the thermostat display

Add a note or more photos next. Nobody calls you.

When to call a pro

The breaker trips again, the unit has power but still won't start, a status light flashes a fault code, or there's a burning smell or any gas odor. For lifespan and upkeep, see the furnace guide.

Typical cost: $100–500 for most no-start repairs including the service call. A diagnostic visit typically runs $50–150, often credited. A blower motor replacement can reach $2,000.

Sources: HomeAdvisor: furnace repair cost (updated June 2026)

After a scan, Fixology can also help you find pros near you.

Related problems

  • Furnace won't heat?

    Furnace

    The furnace runs but the house stays cold, which is usually a clogged filter, a thermostat setting, or an ignition fault.

  • Heat pump not heating?

    Heat pumpFall

    The heat pump runs but the house stays cold, which is usually thermostat settings, a clogged filter, or an iced-over outdoor unit.

  • Washer won't drain?

    Washer

    Water is left in the drum after the cycle, which is usually a clogged pump filter or a kinked drain hose.

  • Fridge not cooling?

    Fridge

    The fridge section is warm or warming. The cause depends on whether the freezer is still cold, and the first fix is often free.

Fixology helps you understand your home — it isn't a substitute for a licensed pro on serious gas, electrical, or structural work.