Furnace Not Turning On? What Spokane Homeowners Should Check First

The first cold morning in October is when we find out which furnaces made it through summer. You turn the thermostat up, wait, and nothing happens. A furnace not turning on after months of sitting idle is common, and a good share of the time the cause is something you can check yourself in ten minutes without opening anything that holds gas or high voltage. This is the order we would check it in.

Why a Furnace Refuses to Start

Most people picture a furnace that will not start as a furnace that has died. Usually it has not. It has refused.

A modern gas furnace runs a strict sequence every time it starts. The thermostat calls for heat. A small inducer fan starts to clear the vent pipe. A pressure switch confirms the venting works. The igniter glows. The gas valve opens. A flame sensor has a few seconds to prove there is a flame, and if it cannot, the gas shuts off. Only then does the main blower start pushing warm air through the house.

Every one of those steps is a safety check, and the control board will not move to the next until the last one passes. When a check fails a few times in a row, the board locks the furnace out. Nothing is broken in the sense of worn out. Something told the furnace it was not safe to run, and it listened.

That is why most cases of a furnace not turning on can be solved with the checks below. Each one clears whatever is blocking a step.

Furnace Not Turning On: 6 Things to Check

1. The thermostat

Make sure it is set to Heat, not Cool or Off, and that the setpoint is at least three degrees above the room temperature. A blank screen usually means dead batteries. If a smart thermostat lost its Wi-Fi or its schedule over the summer, it may simply not be calling.

2. The furnace power switch and breaker

Near the furnace there is a switch that looks like an ordinary light switch. It gets flipped off by accident all the time, often by someone reaching for the basement light. Check it, then check the breaker for the furnace in your panel.

3. The blower door

The front panel on the bottom of the furnace presses a safety switch when it is closed. If the panel was put back slightly crooked after a filter change, the switch never closes and the furnace will not do anything. Take it off and seat it firmly.

4. The filter

A filter that has been in since spring can choke airflow badly enough that the furnace overheats, trips its high limit switch, and eventually locks out. If you cannot see light through it, replace it.

5. The fuel supply

If your stove or water heater runs on gas and they work, your gas is on. Check that the handle on the gas line beside the furnace runs parallel to the pipe, which means open. In parts of North Idaho, such as around Rathdrum, Athol, and Spirit Lake, many homes run on propane, and an empty tank looks exactly like a furnace not turning on for any other reason.

6. The vent pipes and condensate drain

High-efficiency furnaces vent through two white plastic pipes, usually out a side wall. Over the summer, wasps and birds build in them. In winter, drifting snow buries them. Either way the pressure switch cannot prove the vent is clear, and the furnace will not light. Clear them by hand from outside. The same furnaces make water and drain it through a small plastic trap and hose. If that line is clogged or frozen, the furnace shuts down too.

Then reset it, once

Turn the furnace switch off, wait 30 seconds, and turn it back on. That clears a lockout. Before you do, look through the small window on the lower panel. A blinking light there is a fault code, and the chart on the inside of the panel explains it. Write the pattern down or take a short video. It saves a technician time.

What We Do Not Recommend

Do not keep resetting a furnace that locks out again. It locked out for a reason, and repeated restarts can push unburned gas into the burner area or hide a venting problem.

Do not bypass or jumper any switch. The pressure switch, the high limit, and the rollout switch exist to stop carbon monoxide and fire. Disabling one to get heat tonight is the most dangerous thing on this list.

Do not heat the house with the oven. Run space heaters only with clear space around them, and make sure you have working carbon monoxide detectors on every floor.

If you smell gas, leave the house first, then call Avista at (800) 227-9187 or 911 from outside. Do not flip switches on the way out.

When to Call a Technician

Call us if your furnace is still not turning on after the six checks, if it lights and then goes out within a few seconds, if the igniter never glows, if you hear the inducer fan run but nothing follows, or if it locks out again after a reset. Those point to a flame sensor, igniter, pressure switch, inducer motor, or control board, and each one needs testing with a meter before anything is replaced. Our furnace repair team works across Spokane, Spokane Valley, Liberty Lake, Coeur d’Alene, Post Falls, and Hayden.

If you have a heat pump rather than a gas furnace, the checks are different. See our heat pump repair page.

A yearly furnace maintenance visit catches most of these problems before the first cold morning, and our preventive maintenance plan puts it on the calendar for you. You can also request service directly.

Frequently Asked Questions