At this time of year, many of us are preparing our furnaces for the colder months ahead, and this is when we’re likely to notice any issues that require attention. One of the more common problems is that the furnace is not blowing warm air. There are a number of possible causes, such as the pilot light, air filter, gas supply, flame detector, and condensate lines. Some of these issues are easier to detect and fix yourself, and others will require the services of a local professional plumber. In this article, we will examine each potential problem in more detail and offer some advice on how you can resolve them.
Fixing a Damaged Pilot Light
The pilot light ignites the gas burners to ensure that heat can be generated for circulation throughout your home. As you can imagine, this is a critical component, and if it becomes dirty, damaged, or dislodged, it may prevent the entire system from working as intended. This type of problem is more common on older gas furnaces than on newer energy-efficient models. The instruction kit with the gas furnace should have all the information you need to clean or re-light the pilot light.
To fix this problem yourself, locate the pilot assembly and find the reset toggle. This toggle is usually found near or at the bottom of the furnace. Move the toggle to the “Off” position, and the gas flow will be deactivated. Wait at least a few minutes to allow any excess gas that remains in the chamber to dissipate. Next, set the toggle switch to the “On” position to restore the gas supply. Change to the “Pilot” setting to ensure the gas reaches the pilot light and locate the reset button on the furnace. Hold down the reset button as you press the ignitor, or hold a lit match next to the pilot light. A flame should form, and you can release the reset button. Now, the pilot light is lit, and the furnace is ready to generate heat for your home!
Cleaning a Flame Detector
Many modern gas furnaces don’t use a pilot light to start heating. They are reliant on flame detectors to complete the heating cycle successfully. However, these components can become covered in dirt, grime, or dust. These substances can prevent the flame detector from working, and the furnace will lose heat rapidly, blowing cold air into your cold home. This is a pretty wavy fix; locate the flame sensor and clean it thoroughly, and normal operation should be restored. If you’re unsure about working on your gas furnace, it’s good to know that checking the flame detector is also covered during a furnace checkup.
Low Gas Supply
This is definitely out of the purview of most homeowners and DIY enthusiasts. Sometimes a heater that’s blowing cold simply isn’t getting sufficient gas to perform the heating process. This could be a severe problem with your home’s gas supply line or the street’s main line outside. This is not an easy fix; if you suspect this is the cause of the problem, contact your local professional HVAC technician. They will either confirm or deny the cause and, if necessary, will conduct a gas furnace repair project.
The Ductwork is Damaged
The integrity of the ductwork is essential to deliver the treated air (hot or cold) to different rooms in the home. If the ducts are cracked or broken, there may be smaller and larger holes where the treated air is escaping. Although the furnace may generate warm air, it could be released where it does little good, such as in attics, crawlspaces, basements, and other places. So, the air that you receive at the vent will feel colder because the heat has been lost elsewhere. Leaky ductwork is also bad for energy bills because you pay more for wasted energy. A temporary repair using duct tape can fix the problems for a while, but a lasting solution is required. A professional HVAC company can evaluate the condition of your ductwork and fix it for you. In many cases, replacing the ductwork entirely is cheaper, which will improve heating and cooling and reduce your energy bills.
A Dirty Air Filter
The true purpose of an HVAC air filter is to prevent foreign contaminants from entering the sensitive components in the heating and cooling systems. However, the air filter can become covered in dirt, grime, dust, and soot, deleting the airflow. When air cannot move freely through the system, it can become prone to overheating issues. When a furnace overheats, it may begin to blow cold air into your home. To restore normal operations, locate the dirty air filter and replace it with a fresh one.
The Thermostat is Set to “On”
Throughout the year, the seasonal changes will alter how we use our HVAC system to ensure comfortable indoor spaces. You may be surprised to learn that some people forget about the thermostat when the season changes. Think of the thermostat as the brain of the entire HVAC system. If these settings are incorrect, they will fail to deliver the needed performance. A prime example is leaving the thermostat on the “On” setting, which causes the furnace to run continuously. This occurs even if the furnace isn’t producing heat, and it can cause cold air to blow into your home. This is an easy fix: switch the thermostat to the “Auto” setting, and the gas furnace will run during the regular heating process. If you experience problems with your thermostat, regularly clean the sensor to ensure that the component receives the correct temperature data. For the ultimate control, consider switching to a smart thermostat; there may be models that are compatible with your existing HVAC system.
A Clogged Condensate Line
Modern furnaces have condensate drain lines that facilitate moisture removal from your home. If the condensate line is clogged, it can deactivate the gas burners and interrupt the heating process. As a result, cold air can be blown out of the vents, and the condensate drain lines need to be cleaned to restore normal operations. If this is a common problem, talk to your local HVAC company about a condensate drain line upgrade. The cheaper plastic drain lines can be prone to clogging issues and are more likely to develop kinks.
The Heater Needs Time to Warm Up
If you hear the furnace kick on and yet you cannot feel any airflow at the vent or the air feels cold, it may seem like you need to contact your local HVAC technician for help. But this could be normal for your furnace because many models have a fan limit switch. This gives the furnace time to warm up before the blower unit pushes the treated air into the air ducts. Check the owner’s documentation that came with your gas furnace model to confirm that there should be a blower delay after the gas furnace kicks in. If there is a delay, this should only be a few minutes, and if the problem persists, it’s time to contact your chosen HVAC contractor.
The Fan Limit Switch has Failed
The fan limit switch is sometimes referred to as a high-limit switch. This component measures the air temperature within the gas furnace or the hot air supply plenum. It also controls the blower motor functions, and if the switch fails, the blower can operate even if the stove isn’t heating the air. The result is cold air being blown, or the furnace could stop working. This scenario is often highlighted by a blinking LED light on the furnace control board or a thermostat error message. To fix this problem, locate the air filter, clean it, or replace it entirely. The airflow is restricted when the air filter is clogged, and the heat exchanger may become too hot. This can trigger the fan limit switch, and the furnace can be shut down as a safety measure. Contact an HVAC professional if you’ve cleaned or replaced the air filter and the problem persists.
An Electronic Control Board Failure
Many modern furnaces have operations that are managed by an electronic control board. If this crucial component is compromised, the heater may blow cold air into the home, or the temperatures may fluctuate wildly. Some common signs that this is the source of the problem include blinking LED lights, the igniter turning on with no heat, a gas burner “woosh” noise, and the blower fan running for too long. Many electric and gas furnaces have built-in diagnostic systems that will trigger various patterns to make fault finding easier. Sometimes, you may get advice remotely if you can talk to the HVAC company about what you see. Contact a professional HVAC technician if you need to fix or replace a failed electronic control board.