Check the Thermostat First
Set the thermostat to heat, raise the setpoint above the current room temperature, and confirm the display is lit. A dead thermostat battery or a tripped program can prevent the furnace from firing.
Power and Breaker
Check the furnace power switch and the breaker. A tripped breaker or a switched-off furnace switch will stop the unit entirely.
Igniter and Flame Sensor
A cracked igniter or a dirty flame sensor are common no-fire causes. These are internal components a technician should inspect—do not open the furnace burner compartment yourself.
Limit Switch
A tripped high-limit switch shuts the furnace down to prevent overheating, often caused by restricted airflow from a dirty filter.
When to Call a Professional
If the thermostat, breaker, and filter check out and the furnace still won't start, request furnace repair. If you smell gas, leave the building and call your gas utility or 911 first.
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Frequently Asked Questions
Request service
Submit a service request and a coordinator will contact you to confirm technician availability. We do not confirm an appointment until availability is verified.
What happens next: A coordinator reviews your request, confirms the service type and location, and contacts you to schedule.
For emergencies: Call (312) 555-HVAC or request emergency service. For a gas leak or carbon monoxide, leave the building and call your gas utility or 911 first.
Request service
Submit a service request and a coordinator will contact you to confirm technician availability. We do not confirm an appointment until availability is verified.