Furnace not turning on? Start with these.

1. Check the thermostat properly. Confirm it is set to HEAT, not COOL or OFF, and that the target temperature is at least five degrees above the current room reading — a furnace will not fire for a one-degree difference. If the screen is blank, replace the batteries. This is a genuinely common cause and costs nothing to rule out.

2. Check the breaker. Find the furnace breaker in your electrical panel. If it has tripped, switch it fully OFF and then back ON — a half-tripped breaker looks normal but passes no power. If it trips again immediately, stop and call a professional; something is drawing a fault and repeatedly resetting it is a fire risk.

3. Check the furnace power switch. Most furnaces have a switch that looks exactly like an ordinary light switch, mounted on or beside the unit. It gets flipped off by accident during cleaning, laundry or basement work more often than anyone expects.

4. Check the furnace door panel. There is a safety interlock behind the front panel that cuts all power when the door is off. If the panel was removed for a filter change and not seated firmly, the furnace will be completely dead by design. Push it until it clicks.

5. Check the filter. A filter thick with dust chokes airflow, which overheats the furnace and trips a safety limit switch that shuts everything down. If the filter is gray and matted, replace it and give the unit half an hour to cool before retrying.

6. Check the gas supply. Make sure the gas valve at the furnace is open (the handle should run parallel to the pipe, not across it) and confirm other gas appliances still work. If your stove is also dead, the problem is the gas supply, not the furnace. If the house is heated by a heat pump rather than a gas furnace, skip this check entirely — there is no gas valve and no burner, so the no-start fault list is a different one, and the Spokane heat pump repair page covers the reversing valve, defrost and outdoor-unit faults that apply instead.

7. Check the condensate drain. High-efficiency furnaces produce water, and most have a float switch that shuts the furnace off if the drain clogs and the pan fills. A blocked drain or a full pan is a very common winter no-start on newer units.

8. Read the blinking light. Most furnaces have a small LED behind a viewing window that blinks a diagnostic code, with a legend printed inside the door panel. Counting the blinks and reading the legend tells you — and any technician you call — exactly which safety tripped, which shortens the visit and lowers the bill.

Make sure it is really not turning on. Two faults get described as a furnace that will not start when the furnace is in fact starting, and they point at different parts, so it is worth telling them apart before anyone is called. If the burners light and the system shuts itself down a few minutes later, over and over, that is a furnace short-cycling rather than a dead one — usually a clogged filter tripping the safety limit switch. If the blower runs steadily but the air arriving at the registers is cool, the burners are not staying lit, or the thermostat fan is simply set to ON instead of AUTO; the furnace blowing cold air guide walks through which of those it is. A genuinely dead furnace makes no sound at all when you raise the thermostat.

Does your furnace even have a pilot light? Furnaces built before roughly the early 1990s use a standing pilot — a small flame that burns continuously and lights the main burners on demand. Anything newer almost certainly uses an electronic igniter instead and has no pilot at all, so there is nothing to relight. Spokane has a lot of older housing stock, so both are common here. If your furnace does have a pilot and it has gone out, the relighting steps are printed on a label inside the furnace door. If it lights but will not stay lit, the usual cause is a failed thermocouple — the small sensor that proves a flame is present and holds the gas valve open. It is an inexpensive part.

When to stop and call someone. If you smell gas, leave the house first and call your gas utility from outside. If the breaker trips repeatedly, if you see scorching, or if the furnace lights and then shuts off again and again, those are faults that need a licensed technician rather than another reset.

When the eight checks still leave you cold overnight. If none of the above brings the heat back and the house is dropping in freezing weather — especially with young children, elderly, or unwell people at home — that is exactly what 24/7 emergency HVAC dispatch is for rather than waiting for a morning appointment. And if the failure keeps returning after each fix on a furnace fifteen years old or more, it is worth weighing the next repair against a replacement — the new-furnace price guide breaks down what actually moves the number, and what a code-correct install involves covers the sizing and venting work that separates a proper job from the cheapest quote.