Why Won't My Furnace Turn On?

If the furnace won't start, begin with the controls you normally use. Don't start opening the furnace or bypassing safety devices.

Check the thermostat

Make sure it's set to Heat, with the target temperature above the current room temperature. If the thermostat uses batteries, check them.

Check normal household power controls

Look at the electrical panel for a tripped breaker. If a breaker trips again after a reset, stop resetting it. Repeated trips need diagnosis.

Check the filter

A severely restricted filter can contribute to HVAC operating problems. Inspect it and service it according to the manufacturer's instructions.

What if you smell gas?

Stop troubleshooting. Leave the area and follow your gas utility or local emergency authority's instructions. Don't attempt to repair gas valves or combustion components yourself.

When should I call?

Arrange service when:

• The thermostat appears correct but the furnace won't start.
• A breaker repeatedly trips.
• The furnace starts and quickly shuts down.
• You hear unusual noises.
• You notice unusual odors.
• The system behaves differently from normal.

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