If the thermostat is set for heat but the furnace stays silent, starts briefly then stops, or never warms the home, the cause is not clear from that one symptom. Describe what you actually observe to the heating provider.
A short observation sequence
- Thermostat: is its display on, set to heat, and set above room temperature?
- Airflow: is the blower silent, moving cool air, or running normally without warmth?
- Scope: is every room cold, or only one part of the home?
- Timing: did the issue start after a power interruption, a filter change, or another known event?
Only use controls described in your equipment manual and that you can reach safely. Do not bypass a safety switch, repeatedly reset a tripped breaker, open a gas assembly or defeat a lockout.
What a professional may need to distinguish
A thermostat/control issue, loss of power, airflow restriction, ignition problem or safety shutdown can all cause a no-start or short-run complaint. A technician's inspection establishes the cause; this page cannot diagnose it remotely.
When to call
Call when the system still will not heat after simple safe observations, especially in cold weather or where someone in the home is sensitive to temperature. Tell the provider whether the fan runs and whether the thermostat displays a message.
For sustained airflow without heat, see furnace blowing cold air. For winter decisions and safety, read the no-heat guide. Check coverage by street address when booking.