- First check that the thermostat is set higher than the actual room temperature. If you have a programmable thermostat, check that it has fresh batteries.
- If equipped with central air, or the system is zoned, make certain the selector switch is on heat.
- Check that the emergency switch (usually a red switch plate at the top of the cellar stairs or on the side of the furnace) is on.
- If you are familiar with the fuse or circuit breaker panel, see if the fuse is burned or the breaker is tripped. Correct the problem once; if the fuse blows or breaker trips again, call a serviceman.
- If you can access the burner, check the red button on the protecto relay. Older furnaces will have a stack limit switch mounted on the smoke pipe that connects the furnace to the chimney. Push the button one time only. Repeated attempts to fire the burner without ignition can create an explosive condition. If the burner fails to fire and continue running on its own, call for service.