Reasons Why Your Furnace Won't Turn On

Your furnace is a complex piece of equipment designed to produce enough heat for your entire home. When well maintained, a furnace can last more than 20 years. However, if your furnace won't turn on, it might indicate a problem with one or more parts.

If you’re wondering, “Why isn't my furnace igniting?” the answer could be one of several potential culprits. In this article, we'll explore common problems and myths that can cause your furnace to shut down and remain off, including:

• Why it’s (probably) not your pilot light
• Wrong thermostat settings
• Tripped circuit breaker
• Clogged air filter
• Other issues

It's simple enough to replace an air filter or reset the breaker box, but many issues that lead to a furnace shutdown require more experience and expertise to fix. Learn about common furnace issues and when to call an HVAC pro.

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If your furnace won't turn on, should you check the pilot light? Unless your furnace is from the 1980s, the problem likely isn't your pilot light. Most newer furnace models don't have pilot lights. Instead, they have electric igniters that automatically ignite the furnace when needed.

In the 1980s, more homes began to prioritize energy conservation, leading to the standardization of electric ignition furnaces. Unlike traditional pilot lights that constantly use gas to keep a flame burning, an igniter only uses minimal electricity when it's time to trigger ignition.

Before the switch to automated igniters, pilot lights ignited the fuel in the combustion chamber. If the pilot light was out, the furnace wouldn't run. Pilot lights were standard for more than 100 years, and many homes had older model furnaces with a pilot as recently as the year 2000. However, as energy-efficient HVAC equipment became more popular, the transition to electric ignition systems accelerated. This shift not only improved energy efficiency but also enhanced safety, as pilot lights could sometimes be extinguished by drafts or other issues, potentially leading to gas leaks.

If your furnace isn't turning on, one of the common culprits could be your thermostat. If you don't have it set correctly, your furnace won't turn on, no matter how cold it gets in your home. Start by checking to see if the thermostat has power. You may need to put new batteries in to change the settings. Then, make sure the thermostat is set to HEAT and ON. If it's set to cool, only the AC unit will be prompted to turn on and off, meaning your home will never warm up.

If the furnace starts but suddenly stops or runs for a while before cutting off and won't turn back on, check the circuit breaker. If the breaker tripped, you'll see at least one switch that's not aligned with the rest. A tripped breaker prevents your furnace from getting power, which means it won't turn on.

Reset the breaker by switching it to the OFF position and then back to the ON position. Wait a minute or two to see if it trips again. If it does, it's time to have a professional assess your unit to determine what's causing the issue.

An overly full air filter can also cause your furnace to shut off. As your air filter starts to fill, it restricts airflow through the system. Your furnace works by pulling cold air into the heat exchanger and then circulating the air after it has been warmed. If there isn't enough air entering the heat exchanger, your furnace has to run harder and longer to reach the desired temperature in your home.

If a clogged air filter causes the heat exchanger to work too hard, it can overheat. Your furnace then shuts down to prevent the heat exchanger from cracking.

Many other issues can shut down your furnace. If you have a faulty blower motor or electrical issue, your system's safety features will trigger a shutdown. The same is true if there's an issue with your pressure switch or something affecting gas flow. All of these issues require service from a certified professional. A qualified HVAC technician has the expertise and tools to accurately diagnose the issue and perform the necessary repairs, ensuring your furnace operates safely and efficiently. Regular maintenance by a professional can also help identify potential problems before they lead to a shutdown, keeping your home warm and comfortable throughout the heating season.

Our NATE-certified technicians will quickly diagnose and repair your furnace, no matter the brand or model. We offer fair and honest pricing, and all work comes backed by a 1-year parts and a 30-day labor warranty. Call us at 503-538-1950 or click below to request service online today!