Why Won’t My Furnace Turn On? Troubleshooting & Solutions

Why Won’t My Furnace Turn On

As temperatures drop and winter sets in, the last thing you want is for your furnace to fail. If you’re wondering “why won’t my furnace turn on?” you’re not alone. A furnace not turning on is a common issue, but luckily, many solutions are available. Here’s what you need to know to troubleshoot your furnace and get it working again.

Key Takeaways

  • A furnace not turning on is a common problem, especially during cold weather.
  • Troubleshooting steps include checking the thermostat, power supply, ignition system, gas supply, air filter, blower motor, and ductwork.
  • In some cases, it may be necessary to call a professional HVAC technician for further diagnosis and repairs.
  • Regular maintenance, including cleaning and professional inspections, can help prevent future furnace issues.

Understanding the Basics

If your furnace isn’t working, it’s important to understand the basic components and how they work together to provide heat for your home. A furnace typically consists of a burner, heat exchanger, blower, ductwork, and thermostat.

The burner is responsible for igniting the fuel (typically natural gas or oil) and generating heat. The heat exchanger then transfers that heat to the air passing over it. The blower pushes that heated air through the ductwork and into your home. Finally, the thermostat regulates the temperature by communicating with the furnace to turn on or off as needed.

Common Issues

Now that you know the basics, let’s talk about common issues that can prevent your furnace from starting. A faulty thermostat, power supply issues, ignition system malfunctions, gas supply problems, clogged air filters, malfunctioning blower motors, and issues with the ductwork can all cause problems with your furnace.

It’s important to diagnose the issue correctly in order to fix the problem and restore heat to your home. Let’s delve deeper into each of these potential issues in the following sections.

Check the Thermostat

If your furnace isn’t turning on, a faulty thermostat may be to blame. Start by checking the thermostat settings, making sure it is set to “heat” and the temperature is set higher than the current room temperature. If the thermostat seems to be functioning properly, you can try troubleshooting and testing it to make sure it’s working correctly.

First, turn off the power to your furnace. Remove the thermostat cover and make sure the wires are properly connected. If any wires are disconnected or loose, try tightening them and then turn the power back on to see if the furnace starts up.

If the wires are all connected and the furnace still won’t turn on, you can try replacing the batteries in your thermostat. If this doesn’t help, it’s possible the thermostat itself is faulty and needs to be replaced.

Before replacing the thermostat, though, you should double-check that it’s the problem by testing it with a multimeter. Set the multimeter to “Ohms” and touch one probe to the “R” terminal and the other probe to the “W” terminal. If the multimeter reads between 20 and 30 Ohms, your thermostat is working properly. If it reads as “open” or “infinite,” the thermostat is faulty and needs to be replaced.

Check the Power Supply

If your furnace still isn’t turning on, it’s possible that the issue lies with your power supply. It’s important to note that furnaces typically require a dedicated circuit with its own circuit breaker. If the breaker has tripped, your furnace will not receive power and will not turn on.

To check the power supply:

  1. Locate your furnace’s circuit breaker and ensure it is in the “on” position.
  2. If the circuit breaker has tripped, reset it by switching it off and then back on.
  3. Check to see if any fuses related to the furnace have blown. If so, replace them.
  4. Ensure that the furnace is receiving power by checking the electrical panel or meter box for any issues.

If none of these steps help, it’s best to consult a professional HVAC technician, as there could be a wiring issue or problem with the furnace’s electrical system that requires specialized knowledge and equipment to diagnose.

Inspect the Ignition System

If your furnace is not igniting, the problem could lie with the ignition system. There are two types of ignition systems – pilot light and electronic – and each requires specific troubleshooting steps.

Pilot Light Ignition System

If your furnace has a pilot light, the first step is to check that the pilot light is lit. Follow these steps:

  1. Find the pilot light assembly. It is typically located near the burner.
  2. Turn the thermostat to the lowest temperature setting.
  3. Find the gas valve and turn it to the “off” position. Wait at least five minutes for any accumulated gas to dissipate.
  4. Locate the pilot light and hold a flame to it. If it lights, continue to hold the gas valve in the “on” position for an additional minute or two.
  5. Turn the gas valve to the “on” position and turn up the thermostat to see if the furnace ignites.

If the pilot light doesn’t stay lit or doesn’t light at all, there may be an issue with the gas supply, thermocouple, or pilot assembly.

Electronic Ignition System

If your furnace has an electronic ignition system, follow these steps:

  1. Make sure the thermostat is set to “heat.”
  2. Turn off the power to the furnace for at least five minutes.
  3. Turn the power back on and listen for a clicking sound. This indicates that the electronic ignition system is attempting to ignite the furnace.
  4. If you don’t hear a clicking sound, there may be an issue with the ignition control module or flame sensor.
  5. If you hear a clicking sound but the furnace still doesn’t ignite, there may be an issue with the gas supply or gas valve.

If you’re not comfortable troubleshooting the ignition system on your own, it’s best to call a professional HVAC technician.

Check the Gas Supply

If your furnace is not igniting, a gas supply issue may be the culprit. Here’s what you can do to troubleshoot:

  1. Check the gas valve: Make sure the valve supplying gas to your furnace is fully turned on. If it’s off, turn it on and wait a few minutes to see if the furnace ignites.
  2. Check the gas line: Inspect the gas line for any damage, kinks, or punctures. A damaged gas line can disrupt the flow of gas to the furnace and prevent it from igniting.
  3. Check for gas flow: Verify that gas is flowing to the furnace by listening for a hissing sound near the gas line or valve. If you don’t hear any sound, the gas flow may be blocked or restricted.

If you have checked all of these items and the furnace still won’t ignite, it’s time to call in a professional HVAC technician to diagnose and repair the issue. Do not attempt to fix a gas supply issue on your own, as it can be dangerous.

Inspect the Air Filter

If your furnace is not blowing hot air, your air filter may be clogged and preventing proper airflow. Inspect your air filter to determine if it needs cleaning or replacement.

Step Description
1 Locate the air filter. It is typically found near the blower motor or in a slot on the cold air return duct.
2 Remove the air filter from the furnace.
3 Inspect the air filter for dirt, debris, or damage. A clogged filter will be visibly dirty and may even have debris visibly packed into the filter material.
4 If the filter is dirty, clean it by gently tapping it against a hard surface, or replace it with a new filter. Make sure to use the correct size and type of filter for your furnace.
5 Reinstall the air filter and turn on your furnace to see if the airflow has improved.

Note: It is recommended to check and clean or replace your air filter every 1-3 months to ensure proper airflow and efficient operation of your furnace.

Check the Blower Motor

If your furnace is turning on but not blowing hot air, the problem may lie with the blower motor. The blower motor is responsible for circulating air throughout your home, and if it isn’t functioning properly, you may experience poor airflow and uneven heating.

To check the blower motor, start by turning off the power to your furnace. Locate the blower motor and inspect it for any signs of damage or wear, such as loose belts or broken fan blades. If you notice any issues, you may need to replace the blower motor entirely.

If the blower motor appears to be in good condition, you can test it by turning the furnace back on and setting the thermostat to “fan only.” If the blower motor still doesn’t turn on, you may have a faulty relay or control board. In this case, it’s best to call a professional HVAC technician for further diagnosis and repair.

Regular maintenance can help prevent issues with the blower motor. Be sure to clean and lubricate the blower motor and its components as part of your routine furnace maintenance.

Inspect the Ductwork

If your furnace is turning on but not blowing hot air, the problem may lie with your ductwork. The ducts in your home are responsible for distributing heated air throughout each room. If there is an issue with your ductwork, it can prevent warm air from reaching certain areas.

To check for problems with your ducts, start by inspecting them for any leaks, blockages, or damage. Leaks can occur at joints or in areas where the ductwork has become disconnected. Blockages may be caused by debris or buildup inside the ducts. Damaged ducts may be bent or crushed, restricting airflow.

If you find any issues with your ductwork, take steps to address them as soon as possible. Small leaks can often be sealed with duct tape or duct mastic. Blockages can be cleared by removing and cleaning duct covers, or by using a vacuum hose to suck out debris. In cases of significant damage, it may be necessary to replace the affected portion of the ductwork entirely.

Keep in mind that issues with ductwork can also be caused by improper installation or sizing. If you suspect this may be the case, it’s best to consult with a professional HVAC technician.

Call a Professional

If you’ve gone through all of the troubleshooting steps and your furnace is still not working, it may be time to call in a professional HVAC technician. Trying to fix complex issues without proper training and tools can lead to further damage and safety hazards.

When searching for a technician, be sure to choose a licensed and insured professional with experience in furnace repair. Ask for references and check reviews to ensure you’re hiring a reputable company.

A qualified technician will be able to diagnose and repair the issue quickly and efficiently, restoring heat to your home. Additionally, they can provide guidance on preventative maintenance and offer advice on how to avoid future furnace problems.

Regular Maintenance Tips

Regular maintenance of your furnace is key to ensuring it runs efficiently and avoids future issues. Here are some tips to keep in mind:

  • Clean or replace the air filter: A dirty air filter can restrict airflow and reduce efficiency. Check it monthly and replace it every 1-3 months.
  • Lubricate moving parts: Check your owner’s manual for parts that may need lubrication, like the blower motor. Lubricate these parts once a year to prevent wear and tear.
  • Clean the blower: The blower can collect dirt and dust, reducing airflow and efficiency. Clean the blades with a damp cloth and vacuum out the blower compartment annually.
  • Check the ductwork: Inspect the ductwork for leaks, blockages, or damage. Repair any issues to ensure proper airflow and heat distribution.
  • Schedule annual HVAC maintenance: Hire a professional HVAC technician to perform annual maintenance and inspections to catch any potential issues before they become major problems.


Dealing with a furnace that won’t turn on can be frustrating, but don’t give up hope! By following the troubleshooting steps outlined in this article, you can diagnose and fix the problem on your own in many cases.

Remember to start with the basics by checking the thermostat and power supply before moving on to more complex issues like the ignition system or blower motor. Don’t forget to inspect the air filter and ductwork as well, as clogs or obstructions can impact heat distribution.

If you’re not comfortable performing these steps yourself, or if you’ve identified a more serious problem, it’s always a good idea to call in a professional HVAC technician. They can diagnose the issue and make necessary repairs quickly and efficiently.

Lastly, don’t neglect regular maintenance! By taking care of your furnace with simple tasks like cleaning and lubricating, you can help ensure it runs smoothly and avoid future issues down the road. So take action today and get your furnace up and running again!

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