When it’s cold outside, you rely on your furnace to keep your family warm and comfortable. And there’s nothing more frustrating than a furnace that won’t turn on.

So, what do you do if your furnace is giving you trouble? In this blog, we’ll help you troubleshoot your furnace issue by attempting to diagnose the problem without needing to call for professional help.

The most common reasons why a furnace won’t turn on include:

  • The thermostat is set to the wrong settings
  • A tripped circuit breaker
  • A clogged or dirty air filter
  • Broken or malfunctioning components
  • Triggered safety feature

We’ll also explain why certain problems can be fixed by you and which will require the help of a professional HVAC technician.


Want to schedule a furnace tune-up with trusted professionals? Contact Aspire Heating and Cooling: 336-281-0047. Our NATE-certified technicians are trained to service all makes and models and will provide a written report of their findings. If repairs are needed, you can trust that they’re in your best interest only. Our commitment to honesty and integrity is just one of the reasons why we’ve earned so many 5-star customer ratings.

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Your Thermostat Is Set to the Wrong Settings

If you’re having trouble getting your furnace to turn on, the first thing you need to do is check out your thermostat.

When a thermostat that is set to incorrect settings, it can stop your furnace from turning on. Additionally, if the thermostat isn’t connected to power for one reason or another, your furnace won’t turn on either.

First, make sure your thermostat is on and connected to power. If the thermostat’s display screen is dark or appears to be off or unresponsive, something is wrong. This could be simply caused by dead batteries, or something more serious. You’ll want to switch out the thermostat batteries to eliminate a battery issue as the root cause. If you’ve replaced the batteries and your thermostat display is still not responsive, then you’ll likely need to contact an HVAC professional to diagnose the issue.

Second, check to ensure that your settings are set to HEAT and ON. When your thermostat is set to COOL, your furnace won’t turn on even if the set temperature on the thermostat is higher than the current temperature in your home.

If your thermostat is on and responsive and it’s set to the correct settings, but your furnace is still not turning on, you may have a more serious issue, or the issue may not be related to the thermostat.

A Tripped Circuit Breaker

The next thing you’ll want to check is your electrical panel to see if you have a tripped circuit breaker.

Sometimes a power outage, power surge, or an overworking furnace can trip the circuit breaker that’s located in your electrical panel. This can happen during electrical events to prevent electrical currents from rendering damage to your furnace. If your furnace’s circuit breaker has tripped, the power going to your furnace has been cut off and your furnace will not be able to turn on.

To see if this is the issue, go to your electrical panel and check to see if the furnace breaker is flipped to the OFF position. If it is, you can try to reset it:

  1. Locate the switch labeled “furnace” in your electrical panel.
  2. If the switch is in a different position than the rest of the other switches, flip the switch OFF by turning it to the right.
  3. Then, flip the switch to ON by turning it to the left.

Wait 30 seconds to see if the breaker trips again. If your breaker continues to trip, you’ll need to call a professional and schedule a repair appointment. Do NOT try to reset the switch again because you may have more serious electrical issues that need to be fixed.

A Clogged or Dirty Air Filter

While an air filter may sound like a minor component of a furnace, they have a major impact on the efficiency and well-being of your furnace. Dirty or clogged air filters can cause your furnace to overheat. When a furnace overheats, it won’t turn on. We’ll explain.

If your air filter is dirty, the clogged filter can reduce the flow of air entering your furnace. Furnaces pull in air to be heated by a component called the heat exchanger. Once the heat exchanger heats the air, the heated air is then circulated throughout your home through ductwork. This process repeats itself until the air inside your home reaches your desired temperature.

That said, if the clogged air filter is blocking the amount of air entering your furnace, the heat exchanger has to work harder to heat the air and get your home to your set temperature. This overworking can eventually lead the heat exchanger to overheat which will cause your furnace to auto shut down to prevent damage.

To see if you have a dirty air filter, follow the below steps:

  1. Turn your thermostat off to stop your furnace from turning on while replacing your filter.
  2. Remove your current air filter.
  3. Replace the air filter by inserting the new air filter into the slots. Make sure you’re inserting the new air filter by following the arrows on the filter frame. If the air filter is inserted incorrectly, the airflow direction will be wrong.
  4. Turn your thermostat back on to check if your furnace is turning on again. If yes, you can prevent your furnace from shutting down in the future by regularly changing out your air filter.

It is important to regularly replace your air filter every three months or whenever it’s dirty.

Broken or Malfunctioning Components

Furnaces are made up of a variety of components, including:

  • The blower motor
  • Circuit boards
  • Flame sensors (older furnaces)
  • Electronic ignition systems (newer furnaces)

Due to normal wear and tear, components within a furnace can and will eventually fail or malfunction over time. If your furnace has a broken or malfunctioning part, your furnace may not turn on. In this case, a professional HVAC technician will be able to identify the issue and fix or replace any or all broken parts.

Before you call in a professional, you can double-check that your furnace power switch is set to ON. If you’re unsure what to look for, look for a switch (typically located near or attached to the air handler) that resembles a normal light switch. If you notice that the switch is in the OFF position, it’s possible that something may have unintentionally switched it off and you can switch it back ON to see if this solves your problem.

Triggered Safety Feature

The majority of today’s furnaces come fully equipped with safety features designed to prevent dangerous electrical situations and keep your home safe.

Two common safety features on a furnace are the float switch and the flue gas spill switch. If either of these safety features has been activated, it’s very likely that your furnace will not turn on.

If this is the case, you’ll need to call a professional HVAC tech to inspect your furnace, repair the issue, and make sure that your furnace is operating safely and efficiently.

Remember, a defective furnace can increase your energy costs over time, put you and your family in danger, and end up costing you more than just a furnace repair fee.


Need Furnace Maintenance in the Mocksville or Winston-Salem Area?

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Aspire Heating and Cooling provides trusted HVAC services to Mocksville and Winston-Salem residents.

Aspire Heating and Cooling provides trusted HVAC services to Mocksville and Winston-Salem residents.

Call Aspire Heating & Cooling at 336-281-0047 or request an appointment online. We’ll dispatch one of our skilled HVAC technicians to thoroughly inspect, clean, and optimize your furnace. Plus, we offer upfront prices, honest guidance, and back up our work with a 100% satisfaction guarantee. To learn more about what to expect when you hire us, visit our heating maintenance page.

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