Key Points
- Furnaces warm your home by using fuel and a heat exchanger to disperse warm air throughout your home.
- Some furnace complications can be fixed by the homeowner, but many will require a licensed professional.
- Annual maintenance is integral for furnace safety. Carbon monoxide is a dangerous byproduct of the fossil fuels used by furnaces, which can leak inside the home without proper upkeep.
Picture this: It’s the middle of a harsh winter. Your furnace has been hard at work for weeks, keeping your home supplied with toasty temperatures. You wake up in the morning after a cold front pushes through your area, expecting the same cozy conditions, only to see the puff of your hot breath in the frigid air as you let out a big yawn. Whether you hear your HVAC system running or not, it clearly isn’t working as expected anymore.
Technology is wonderful until it isn’t working as expected. HVAC systems can stop working for a wide variety of reasons. Issues like a lack of gas supply or a tripped breaker can prevent the furnace from receiving the energy it needs to operate. Leaking ducts or a clogged air vent might stop your system from maintaining efficiency. Malfunctions from the thermostat can even interfere with how effectively the system distributes warm air. If your furnace starts to struggle, these troubleshooting tips can help you identify and repair the issue. Read on to learn how to check in on your furnace and what kind of maintenance you can perform to restore consistent climate control.
How Do Furnaces Work?
Furnaces heat your house using two key components: fuel and a heat exchanger. The types of fuel furnaces run on include electricity, oil, coal, wood, and gas, though gas-burning furnaces are by far the most common. Beyond these two pieces, furnaces contain a myriad of additional parts. These include:
- Thermostat
- Gas valve
- Ignitor and flame detector
- Combustion air intake
- Burners
- Transformer
- Blower fan
- Air filter
- Supply-air plenum
- Return-air plenum
- Heat exchanger
- Exhaust pipe
A home's gas supply is outside, and a pipe connects the storage tank or local gas supply network to the furnace inside. When gas enters a furnace, a burner lights it to allow the fuel to heat incoming cold air in the heat exchanger. The furnace's gas valve regulates the incoming gas pressure, while the combustion pipe exhausts any gases via a vent and an exhaust pipe that safely releases the byproducts created during combustion outside. Thermostats detect the temperature in each room, using a blower fan to direct heated air throughout the home to where it’s needed. As the plenums send warm air to the ducts and the blower fan distributes heat, the return ducts redirect cold air back into the furnace, and the room's internal temperature increases.
The heat exchanger in a furnace ensures safe and reliable function by separating the combustion process from the air the blower fan emits. Fuel heats up the exchanger, then the system blows the cold air from your home across the heat exchanger to absorb this heat. The air then travels back into the house to warm you up. Your duct system is essential for your furnace to operate effectively; all that warm air needs to be evenly distributed to create a warm environment. When a thermostat senses that a room has reached its set temperature, it cuts off the warm airflow by switching off the furnace's gas valve to avoid overheating.
What Does It Mean When a Gas Furnace Turns on but There's No Heat?
Does your furnace run, but your home lacks heat? Then the problem is most likely with the ignitor. A furnace will still circulate air like normal without a working ignition, but it won't be able to adequately heat the air. This means that, without ignition, the blower motor will use up energy to push lukewarm air through your home. The furnace needs an ignition to heat the air it distributes, and the ignitor is the part responsible for creating that spark. If you notice cold air circulating throughout your home, check the thermostat and gas valve to ensure they are both working properly. You may need to relight the pilot light to restore a heat source to the furnace's distributed air. If these troubleshooting tips do not do the trick, contact a professional technician for assistance.
What Would Cause a Furnace Not to Kick On?
Furnaces are typically reliable heat sources, but any could fail to perform as expected for a wide range of reasons. Whether your furnace stopped working overnight or you feel lukewarm or cold air coming through the vents in specific areas in your home at some point, understanding typical furnace issues and how to troubleshoot them can help you keep your home comfortable. Some of the most frequent reasons for subpar heating results are:
- Clogged air filter
- Lack of gas supply
- Extinguished pilot light
- Closed or blocked vents
- Leaking ducts
- Faulty power source
- Malfunctioning thermostat
- Incorrect thermostat readings
- Damaged or broken parts
Check the Air Filter
The air filter in your furnace is the first component you should check if your system stops working. Furnace filters collect dust and dirt over time, clogging and causing complications such as hindered airflow and decreased indoor air quality. In some situations, a clogged filter stops a furnace from operating altogether. This level of excessive dirt and dust buildup in the filter can also cause premature breakdowns or fires, so cleaning and replacing it as needed is essential. Check your furnace filter once a month, or every 30 days, with the following steps:
- Turn your thermostat and furnace switch off: You should always power your entire system down before working on it.
- Remove the filter and hold it up to a light source: Holding your filter up to the light is a quick way to check for clogs. If the light does not shine through, you should clean or replace the filter.
- Install a new filter: To install a new filter, make sure its arrows point in the airflow direction.
- Return the access panel: After replacing or cleaning your filter, secure the access panel over it.
Check the Gas Supply and Pilot Light
Your furnace can also stop working if the pilot light goes out or it loses connection to the gas supply. Check the gas valve outside your home to ensure the switch is parallel to the gas line. You can also check your gas supply by turning on other gas appliances in your home: if those still work, the furnace is the problem. If not, ensure your gas supply has the correct connections or call the utility company for assistance.
If your furnace flame is out, you’ll need to relight the pilot. It's crucial to check your furnace's owner's manual before relighting the pilot so you follow the proper steps. Before bringing an open flame near the unlit pilot, turn the gas supply off and wait 10 to 15 minutes. Smell the air to check if any gas odor lingers: if you still smell gas, evacuate your home immediately and move a safe distance away before calling the fire department and contacting your gas company. A lingering gas odor may indicate a leak, a danger that can lead to an explosion if the gas is ignited by a single spark. If there is no gas odor 10 to 15 minutes after turning off your gas supply, you can follow your owner's manual's directions to carefully light the pilot.
Check the Vents and Ducts
Does hot air come out of your air vents, but you still find intermittent cold spots? Your furnace's air ducts could need some attention. Air ducts contain protruding handles known as dampers, which control the system's airflow. The dampers should be fully open for proper airflow, meaning some may need to be opened if you find inconsistent temperatures in your home. Move any furniture, drapes, wall art, or plants that may be blocking your vents to test with unobstructed airflow.
In the event that you notice an entire room or multiple rooms are colder than they should be with your chosen settings, the system's ducts may be leaking, blocked, or improperly designed to hinder airflow. You can locate leaking or blocked ducts by inspecting the system's accessible ducts. Check for gaps between sections and points that branch out, making sure to seal any open gaps with metal duct tape. Even if this patchwork helps, you should also contact a qualified professional to clean and repair your ducts with a more permanent fix. Leaking or blocked ducts are severe complications that lead to a significant increase in your energy bills, so it's essential to address them as soon as they’re identified.
Check the Electrical Panel
Your furnace's power source can also cause it to stop working. Before checking your furnace's power source, make sure your feet and hands are 100% dry, as you will be interacting with electrical hardware. Check the furnace switch near the furnace to make sure it's on; someone could have bumped it and accidentally turned it off. In this instance, you only need to turn it back on to restore functionality. To prevent injury, contact a qualified electrician if you notice any signs of moisture or electrical damage in your system.
If you flip the switch and the furnace still doesn't work, you may need to check the electrical panel. Check the fuse or breaker box to ensure the power is on, following it up with the HVAC breaker if nothing catches your eye. If your electrical panel has labels, you can use them to find your breaker; panels without labels require you to find the switch that points in the opposite direction of the rest. Once you find this outlier, switch it back in the same direction as the others to turn it on. You may also need to reset your breaker afterwards, flipping the HVAC switch completely off and on again. If you hear a click, you have successfully reset the breaker!
In some situations, you may need to re-power a fuse box. To restore power, examine the fuse box for a discolored and melted fuse. Unscrew this fuse and replace it with an identical one. You can take your melted fuse to the store to help you find a replacement that perfectly matches the original. After restoring power, turn the furnace switch on to check if the system works. Contact a professional if the breaker continues to shut down or the furnace's power is still out.
Check Your Thermostat
Troubleshooting potential thermostat complications can also return your furnace to peak performance if your thermostat is malfunctioning or programmed incorrectly. First, ensure your thermostat is on the “heat” setting. Once it is, adjust the temperature to five degrees warmer than the room's current temperature. Replace the thermostat's batteries if necessary, and give it a wipe-down to remove dust if you have an electromechanical thermostat. You can use an object such as a soft paintbrush to lightly brush away dirt and debris.
It's also important to check your thermostat's location. If your furnace is not turning on with the thermostat, it may be reading too much heat. Heat sources such as space heaters, lamps, ovens, and sunlight can cause thermostats to receive false readings about the temperature. Make sure your thermostat is receiving the correct input so it can send out the correct output.
Turn the Furnace Off and On Again
Sometimes, a simple reset can fix your furnace. Try turning your furnace off and back on again to see if this restores your heat. Each furnace is different, so follow your owner's manual to properly reset the system.
Call for a Professional
Some furnace issues require professional maintenance. If your system has a damaged or broken part, diagnosing it can be challenging unless you know what you're looking for. A qualified technician can identify and repair HVAC system issues with skill and precision. Always ensure your home has a backup heat source so you can stay warm when your furnace needs maintenance. An alternative heat source and plenty of blankets can help you and your family stay cozy if you ever need to schedule maintenance and leave the system off while you wait for repairs.
Need a place to purchase replacement parts? We’ve got you covered. Call in to speak with a dedicated parts expert, or check out our newest feature: BOM diagrams. With these diagrams, you can easily find every part necessary for your unit.
How Should I Maintain My Furnace and Keep My Home Safe?
Maintaining your furnace and following safety guidelines prevents damage and injury to your home and loved ones. It can also help you extend your furnace's lifespan. To care for your furnace and keep your home safe, consider the following tips:
- Keep the surrounding area free of flammable items
- Remember to change the air filter regularly
- Schedule annual maintenance by a professional technician to make sure your system is running smoothly
- Keep at least two-thirds of your home's heat vents open to prevent excessive heat from building up in the furnace
- Keep your home's heat vents clean, and avoid obstructing them with furniture or objects
- Install at least one carbon monoxide detector in your home and test it monthly
- Check or replace your CO detector's batteries at least twice a year
Keeping flammable items away from your furnace is crucial. Since a furnace operates on gas, nearby flammable items can pose a serious fire hazard. Regularly changing your air filter can prevent your system from clogging, and scheduling routine maintenance allows a technician to identify potential issues before they lead to real damage. You should always keep at least two-thirds of your vents open so heat can disperse throughout your home instead of accruing in the furnace. It's essential to keep the vents clear of obstructions and free of dust and debris.
Your furnace disperses exhaust outside your home to keep the indoor air clear of gases like carbon monoxide. However, you should still have one or more CO detectors in your home to alert you if there is a leak. CO safety should always be high on your priority list when you burn fossil fuels in your home. Carbon monoxide poisoning can cause severe health complications and death, so evacuate your house immediately and call 911 if your detector goes off.
Invest in a New Furnace With IWAE
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