Furnace not turning on

Check the easy things before you call anyone: the thermostat is set to heat and calling for it, the furnace power switch and breaker are on, and the filter is not clogged. The videos here run five checks on a gas furnace and show cleaning a flame sensor when the burners light and then shut off.

Turn the power off before opening the furnace panel. Cleaning a flame sensor is a small job, but it works near the burners and the gas valve. If you smell gas, leave the house and call your gas company or 911 from outside. Read when to call a licensed pro, and see change a furnace filter first.