Gas Furnace — No Heating
Check heating mode, the thermostat fan setting, filter condition, and open registers when a gas furnace is not heating.
If your gas furnace is not heating, begin with the thermostat settings and airflow. Keep troubleshooting to these simple observations:
- Set the thermostat to HEAT or AUTO and choose a temperature above the current room temperature.
- The fan can be set to ON for continuous airflow or AUTO to run with the heating system; raise the heat setpoint to see whether the system responds.
- If airflow seems weak, check whether an accessible filter is extremely dirty. A clogged filter can restrict airflow; follow the filter and equipment instructions when replacing it.
- Check that registers are open and not blocked.
Do not open the furnace, adjust gas controls, or inspect or relight ignition components. If these basic checks do not help, request service from a qualified technician. If you smell gas, leave immediately and contact emergency services and your gas utility from a safe location.