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A furnace not turning on can be a real headache, especially during the cold winter. It can leave you feeling frustrated and wondering what the problem could be. A malfunctioning furnace can lead to discomfort, inconvenience, and even safety hazards. There are many reasons why your furnace may not be turning on, ranging from simple to complex issues. Before you panic and call for professional help, it’s essential to understand the common issues that can cause a furnace not to turn on. In this article, we will explore some of the most common issues why your furnace won’t turn on and what you can do to fix them.

Thermostat Malfunction 

A malfunctioning thermostat can be a common cause of a furnace not turning on. A thermostat is a device that controls the temperature in a room and signals the furnace to turn on or off accordingly. If the thermostat is not working properly, it can prevent the furnace from turning on even if the furnace itself is working fine. Here are some steps to troubleshoot a thermostat when the furnace won’t turn on.

  • Check the thermostat settings: Make sure that the thermostat is set to “heat” and that the temperature setting is higher than the current temperature in the room. If the thermostat is set to “off” or “cool,” it will not signal the furnace to turn on.

  • Replace the batteries: If the thermostat is battery-powered, check if the batteries are low or dead. Replace them with fresh batteries and see if the thermostat works correctly.

  • Check the wiring: The thermostat is connected to the furnace through a series of wires. Make sure that the wires are securely connected and not loose or frayed. If the wires are damaged, they may need to be replaced.

  • Clean the thermostat: Dust and debris can accumulate inside the thermostat and interfere with its functioning. Clean the thermostat with a soft brush or compressed air to remove any dirt or debris.

  • Reset the thermostat: Sometimes, resetting the thermostat can fix the issue. Turn off the power to the furnace and remove the thermostat from its wall plate. Wait for a few minutes and then reattach the thermostat to the wall plate and turn the power back on.

  • Replace the thermostat: If none of the above steps work, it may be time to replace the thermostat. Choose a thermostat that is compatible with your furnace and has the features you need, such as programmable settings or Wi-Fi connectivity.

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Dirty Air Filters

A dirty air filter can restrict airflow to your furnace, causing it to overheat and shut off automatically. One of the most common reasons for a furnace not turning on is a dirty or clogged air filter. It’s recommended to clean the air filter once a month and replace the air filter every 1-3 months to ensure the proper functioning of your furnace.

What is an Air Filter?

An air filter is a crucial component of your furnace’s HVAC system. It is responsible for filtering the air that passes through your furnace, removing dust, dirt, pollen, and other contaminants from the air. This ensures that the air circulating in your home is clean and healthy.

Over time, the air filter in your furnace can become dirty and clogged, restricting the airflow and making it harder for your furnace to heat your home. A dirty air filter can cause your furnace to work harder, leading to increased energy consumption and higher utility bills. It can also cause your furnace to overheat, which can lead to system failure.

How to Clean Your Air Filter

Cleaning your air filter is a simple task that can be done in just a few minutes. Follow these steps to clean your air filter:

  1. Turn off the furnace: Before you start cleaning your air filter, make sure to turn off your furnace to prevent any accidents.

  1. Locate the air filter: The air filter is usually located on the side or bottom of your furnace. Consult your furnace manual if you’re having trouble locating it.

  1. Remove the air filter: Once you’ve located the air filter, remove it from the furnace. Be careful not to damage the filter or the surrounding components.

  1. Clean the air filter: Use a soft-bristled brush or vacuum cleaner to remove any dust or debris from the air filter. Be gentle, as you don’t want to damage the filter.

  1. Reinstall the air filter: Once you’ve cleaned the air filter, reinstall it in the furnace. Make sure it’s securely in place and facing the correct direction.

How to Replace Your Air Filter

If your air filter is too dirty or damaged to clean, you will need to replace it. Here are the steps to replace your air filter:

  1. Turn off the furnace: As with cleaning the air filter, make sure to turn off your furnace before you start replacing the air filter.

  1. Locate the air filter: The air filter is usually located on the side or bottom of your furnace. Refer to your furnace manual if you’re unsure where to find it.

  1. Remove the air filter: Once you’ve located the air filter, remove it from the furnace. Make sure to note the direction of the airflow before removing it.

  1. Purchase a new air filter: Take the old air filter to your local home improvement store to find a replacement that matches the size and type of your old filter.

  1. Install the new air filter: Insert the new air filter into the furnace, making sure that it’s facing the correct direction. Secure it in place.

  1. Turn on the furnace: Once you’ve installed the new air filter, turn on your furnace and test it to make sure it’s working correctly.

Plano TX Furnace Not Turning On

Ignition Problems

The furnace’s ignition system is responsible for starting the combustion process. If it’s not working correctly, your furnace won’t turn on. A faulty ignition system is a common issue why a furnace won’t turn on. Follow this troubleshooting process of your furnace ignition system to help you identify and fix the problem.

  1. Check the Power Supply

Before we dive into the ignition system, let’s make sure your furnace is receiving power. Start by checking the circuit breaker and making sure it is not tripped. If it is, reset it and see if that solves the problem. Also, check if the furnace switch is turned on. If neither of these is the problem, move on to the next step.

  1. Check the Thermostat

Next, check your thermostat. Make sure it is set to heat and the temperature is set above the current room temperature. If you have a programmable thermostat, make sure the settings are correct. If the thermostat is not the problem, move on to the next step.

  1. Check the Ignition System

Now it’s time to check the ignition system. There are two types of ignition systems: a standing pilot and an electronic ignition.

Standing Pilot Ignition System

If your furnace has a standing pilot ignition system, check to see if the pilot light is on. If it is not, follow these steps:

  1. Turn off the furnace’s power supply.
  2. Locate the pilot light assembly, which is usually located near the burners.
  3. Turn the gas valve to the off position.
  4. Wait a few minutes to allow any gas to dissipate.
  5. Turn the gas valve to the pilot position and press down on the reset button while lighting the pilot with a match or lighter.
  6. Hold down the reset button for 30 seconds, then release it.
  7. Turn the gas valve to the on position and turn the furnace’s power supply back on.

Electronic Ignition System

If your furnace has an electronic ignition system, it will have either a hot surface igniter or a spark igniter. Check the following steps to troubleshoot the electronic ignition system:

  1. Turn off the furnace’s power supply.
  2. Remove the furnace cover panel to access the ignition system.
  3. Inspect the hot surface igniter or spark igniter for any visible damage. Replace it if necessary.
  4. Check the flame sensor for any dirt or debris. Clean it with a soft-bristled brush.
  5. Turn the furnace’s power supply back on and observe the ignition system for any signs of ignition.

  1. Check the Gas Supply

If the ignition system is not the problem, it’s time to check the gas supply. Start by checking the gas valve to make sure it is turned on and check the gas line for any leaks or damage. Suspected a gas leak, turn off the furnace’s power supply immediately and contact a professional to inspect and repair the gas line.

  1. Call a Professional

If you have followed all of the troubleshooting steps and your furnace still won’t turn on, it’s time to call a professional HVAC technician. They will have the expertise and equipment to diagnose and repair the problem.

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Faulty Blower Motor

The blower motor is responsible for circulating air throughout your home. If the blower motor isn’t working, your furnace won’t be able to push hot air through your vents. A faulty belt, motor bearings, or an issue with the control board could cause a faulty blower motor. Here is how to troubleshoot your blower motor, so you can get your furnace working efficiently and effectively.

  1. Check Your Thermostat

The first step to troubleshooting your furnace is to check your thermostat. Ensure that it is turned on, and the temperature is set to a level that is higher than the current room temperature. If your thermostat is battery-operated, make sure that the batteries are not dead. For a thermostat that is wired, ensure that the wires are not loose or disconnected.

  1. Check Your Circuit Breaker

If your thermostat is working correctly, the next step is to check your circuit breaker. Locate your furnace’s circuit breaker and check if it has tripped. Now it is time to reset it and wait for a few minutes to see if the furnace starts. Your furnace may be experiencing a more serious problem if it won’t start.

  1. Check Your Air Filter

A dirty air filter can cause your blower motor to malfunction. The clogged air filter can cause your furnace to overheat and shut off. If the air filter is dirty it can also restrict the airflow, causing your furnace to work harder than necessary. Check your air filter and replace it if it is dirty.

  1. Check Your Blower Motor

If you have completed the above steps and your furnace still won’t turn on, it’s time to check your blower motor. The blower motor is typically located in the furnace’s air handler. Turn off the power supply to your furnace and remove the access panel to locate the blower motor. Check if the blower motor is clean and free from debris. If it is dirty, use a soft brush to clean it.

  1. Check Your Capacitor

The capacitor is responsible for providing an initial boost of power to the blower motor. If your blower motor isn’t turning on, it could be due to a faulty capacitor. Locate the capacitor in your furnace’s air handler and inspect it for any signs of damage, such as bulging or leaking. If you notice any damage, replace the capacitor immediately.

  1. Check Your Bearings

Over time, the bearings in your blower motor can wear out, causing the motor to malfunction. To check the bearings, turn off the power supply to your furnace and remove the access panel to locate the blower motor. Check if the bearings are worn out, and if they are, replace them.

  1. Check Your Belt

If your furnace’s blower motor is connected to a belt, check if the belt is in good condition. A worn-out or broken belt can cause your blower motor to malfunction. If the belt is worn out, replace it immediately.

Fuel Supply Issues

Your furnace may not turn on if it’s not getting enough fuel to ignite. Ensure that your fuel supply is turned on, and the fuel tank has enough fuel. If you’re using propane, check to see if the tank is empty and if it is, refill it.

For a gas furnace, check your pilot light. If the pilot light goes out or doesn’t stay lit, there may be a problem with your thermocouple or thermopile—these are the parts of your heating system that control how much gas flows into your furnace. You can reset them by turning off your power at the main panel and then restarting it after about 15 minutes. This will cause them to reset themselves and start working properly again.

If none of that works, try cleaning out any debris from around the burner intake ports on top of your furnace’s blower housing unit (this is where cool air goes in). This will ensure that heat gets distributed throughout your home evenly instead of being concentrated in one area or another due to blockages from dirt or dust buildup.

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Circuit Breaker Tripped

If your furnace isn’t turning on, it could be because the circuit breaker has tripped. Check your circuit breaker to see if the furnace’s breaker has tripped and if it has, reset it. You might need to get in touch with a pro to look into the problem if the circuit breaker keeps tripping.

The most common cause of a tripped circuit breaker is overloading your home’s electrical system. This can happen when too many appliances are plugged in at once or if one or more of your appliances malfunctions and draws more power than its intended capacity.

If you’re experiencing issues with your furnace not turning on, try using only one major appliance at a time while waiting for help from a professional.

Faulty Limit Switch

The limit switch is responsible for turning off the furnace when it reaches a certain temperature to prevent overheating. If the limit switch is faulty, it may shut off the furnace prematurely. Fixing a faulty limit switch can be a straightforward process. However, if you’re not comfortable working with electrical components, it’s best to call a professional HVAC technician.

  1. Turn off the power

Before you start working on your furnace, turn off the power to it. You can do this by turning off the circuit breaker that controls your furnace or by switching off the power switch located on the furnace.

  1. Locate the limit switch

The limit switch is typically located on the furnace’s blower assembly. It will have two wires connected to it.

  1. Test the limit switch

To test the limit switch, use a multimeter to check the continuity of the contacts. If there is no continuity, the limit switch is faulty and needs to be replaced.

  1. Replace the limit switch

To replace the limit switch, disconnect the two wires connected to it and remove it from the blower assembly. Install the new limit switch and reconnect the wires.

  1. Test the furnace

After replacing the limit switch, turn on the power to the furnace and test it to ensure that it’s working properly.

Blocked Exhaust Vents

If your furnace isn’t turning on, it could be due to blocked vents. When your furnace is running, it creates exhaust that needs to be vented outside of your home so that it doesn’t build up and cause issues for you and your family. If you have a blocked vent or a vent that is not properly connected, this can prevent the furnace from turning on.

To check for blockages in your vents, look for any obstructions such as snow or debris. If there are any obstructions in the vents, clear them out so that your furnace will be able to run properly again.

Faulty Control Board

Is your furnace not turning on? The control board is responsible for controlling the furnace’s functions, such as the fan and ignition system. If the control board malfunctions, it can prevent the furnace from turning on. A professional technician should inspect and replace the control board if needed.

A faulty control board will not cause any damage to your furnace, but it can be dangerous if left unchecked. If you’re experiencing problems with your heating system, contact a professional technician to help you diagnose and repair your system.

Old Age

Furnaces typically last between 15-20 years. If your furnace is nearing the end of its lifespan, it’s time to consider what your next step will be.

In order to figure out how old your furnace is, you can look at the model number on the unit. This should be located on a plate in front of the unit or in an owner’s manual. You can also check with your local utility company—they should have records of when they installed your furnace.

If your furnace is at or near its expiration date, don’t put off having it replaced. These units are expensive and need to be maintained regularly. If you don’t replace yours when it reaches this age, you may end up with a broken-down system that stops working entirely. This means that not only will you have to pay for repairs, but also for emergency services if there isn’t another source of heat available in your home during cold weather months.


All in all, tackling a furnace that’s not turning on can be an intimidating task, but we hope this guide has been helpful in navigating the steps to help diagnose and solve the issue. If you’re ever feeling overwhelmed or are unable to fix it yourself, never hesitate to reach out for professional assistance.

When it comes to any furnace issues, we understand that you want an experienced and knowledgeable HVAC technician that can efficiently get the job done right. At GO Heating, Air & Plumbing, our team of experienced experts are committed to providing exceptional quality service and delivering projects on time. We have the necessary tools, experience, and knowledge to undertake any size project you need. Plus, whether it’s emergency installation or repair services, our dedicated technicians will be there when you need them most. 

So if you’re experiencing a furnace issue and require quality service with excellent results then contact GO Heating, Air & Plumbing today! Our friendly and knowledgeable staff is here to help ensure your home or business receives the best service possible.

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