If your ducts are leaking (and ENERGY STAR says that almost all homes leak about 30% of the air in their ducts), cold outside air is making its way into your ductwork. Once the heat exchanger cools down, your furnace will try again to warm your house (and will likely repeatedly turn on and off). If your furnace is blowing cold air, or is not operating at all, a component called the fan limit switch may have malfunctioned. Without the cooler air of your home flowing through it and keeping the temperature steady, it will continue to burn hotter and hotter, reaching a temperature of 180-200 degrees. Check your air filter. This “hot then cold air” sequence happens over and over and your home isn’t warming up. Have a technician inspect your air ducts for leaks and provide the best solution. If your furnace continues to blow cold air then you should check if you have a two-stage furnace. If your furnace is blowing cold air, not blowing any air at all, or making odd noises, it’s important to schedule a repair as soon as possible. Is the Pilot Light lit? If you notice your furnace only blows cold air on occasion but your home is still maintaining its temperature than this may be simply a setting on your thermostat. So, if you have a tripped breaker, the furnace may stay on however, the air can’t warm up because the gas burner can’t ignite. Is your furnace not blowing hot air? Here in the New York City area, we’re all pretty tired of the cold weather by now. If you haven’t done that yet this winter, call in an HVAC service expert to keep your system in top shape and prevent unexpected failures. If so, someone may have been too... 2. Check that all supply vents are open. Wait a few minutes, then restart. If you’re still not getting warm air from your furnace, we can help. 6. If this doesn’t fix your problem, and your furnace is still not blowing hot air, you can move on to some of the other potential culprits. December 16, 2020. Turn off power to the furnace at its ON/OFF switch. Why Is My Furnace Blowing Cold Air? Your supply vents (pictured below) push warm air into your home. Or, if your system has not been cleaned in a while, a valve could be stuck due to dirt and debris. Meanwhile, you’ll get cold air because the fan continues to run as a safety measure, even after the furnace isn’t producing heat. This usually arises if you haven’t changed your air filter routinely. If you know how, you can clean or replace the filter yourself, but it’s messy and not as easy as an air filter so you may want to leave this job to the pros. All Rights Reserved. Incorrect thermostat setting. If leaks are excessive, you may want to consider sealing your ducts. The furnace is blowing cold air. What’s wrong? Your furnace blowing cold air could be caused by hot air escaping through holes in the duct work that carries the heat throughout your building. 2. If the filter looks like the filter to the right in the picture below, replace it. Many of the causes of furnace problems can be prevented with regularly-scheduled cleaning and maintenance. We use cookies to give you the best possible experience on our website. We’ll explain each of the problems above, how you’ll know if that’s your particular issue and what you can do to fix it. Try changing the batteries. This can cause the air to … If you have an oil-fired furnace, you may be out of fuel. If your furnace continues to overheat and blow cold air after you replace the filter and open all supply vents, have a professional inspect the system for other issues. Make sure your thermostat is set to HEAT and your fan is set to AUTO. If the furnace burner itself is neglected, accumulated dust and grime can cause trouble igniting. If you have a newer furnace with an electronic control panel, you may need to reset the system. A furnace that isn’t getting fuel will not ignite and will blow only cold air. That may be a quick and easy fix. Even worse, the furnace is blowing cold air! This is sometimes easily solved by resetting the system. Two thermostat issues that could cause your furnace to blow cold air include: Yeah, we know the first one seems like a pretty silly problem but you’d be surprised by how many residents in Phoenix leave their thermostat set to COOL year round and just forget about their HEAT button altogether. Try changing the air filter and restarting the furnace. Your furnace’s limit switch, which specifically works as a safety measure, has turned your furnace burners off until the unit reaches a safe temperature. Naturally, all heaters use a fan to blow air, but if your fan setting is set to ‘on’ throughout the day, it explains why the heater seems like it has malfunctioned. A furnace that blows cold air could also indicate that it is overheating. 2. If your forced-air gas furnace is blowing cold air, a number of factors could be to blame—many of which you can address on your own, without the immediate help of a service professional. If the filter becomes clogged, the unit can start to overheat and cause the burner to shut down. © 2021 Patrick Riley, LLC. Other thermostat issues. 13 reasons your furnace is blowing cold air 1. If you have a gas furnace, a lack of fuel will cause the pilot light to go out. If your furnace is blowing cold air, check your thermostat, air filter and ductwork. The stat is reading at 19 but I have it set - Answered by a verified HVAC Technician. Have you changed your air filter lately? But here are 3 common causes you can fix yourself. If your furnace seems to be blowing cold air, it could be a problem with the ignition system. Large holes and leaks in air ducts can make it seem like your furnace … How Does Workplace Ventilation Impact Employee Productivity? If your fan only runs when your furnace is heating the air, then you’re much less likely to experience your furnace blowing cold air. 3. This can cause your furnace to lock down for safety. Have an expert inspect your ducts along with the furnace. Read on to learn the 13 most common reasons for your furnace blowing cold air and when to call for a furnace repair. This is usually a simple fix, but you’ll need to call a technician to adjust or replace it. So what’s the problem? It’s common for a furnace to blow cold air when you turn it on for the first time each season, but it can also happen at any time if something goes wrong. From dirty air filters to broken thermostats, these are the most common causes of problems. If you have a newer furnace with an electronic ignition, such as an intermittent pilot or a hot surface ignition, your system may need adjustments or replacement of failed parts. It’s a chilly problem that no one should have to deal with during winter in the Atlanta area! In some cases, you may be able to fix the problem yourself. Here’s another possible DIY fix for your heater blowing cold air. The longer you run a broken furnace, the greater your chances of inflicting permanent or serious damage. When the chilly weather finally arrives, and you have to turn on your furnace for the first time after many months of non-use, the last thing you want to find is that it’s not working. If your issue continues, call our team in Tacoma, WA. Leaks in your ductwork means that cold, unconditioned air from inside your attic gets sucked into your ductwork. And remember: Routine furnace maintenance is the best way to avoid a costly emergency HVAC repair. Have your system professionally cleaned to take care of this problem. The thermocouple is a sensor that controls the gas valve and ignition. Again using Occam’s Razor, we can assume that the next likely culprit for your heater blowing cold air is your thermostat. If everything seems to work properly, and then your furnace blows cold air back and forth until it switches off, you may be faced with a furnace that has overheated. Do you have thermostat wars going on in your office? If your furnace starts blowing warm but then quickly turns cold, the flame sensor may need attention. So, once a heating cycle ends and the furnace burners cut off, the fan continues to blow. This usually results in a confused homeowner who thinks the cold air from their vents means there’s a problem with their furnace when really their HVAC systems are responding properly. Go to your thermostat. Pilot Light. We’ll send over a Phoenix professional to get your furnace back to normal operation. To help cool the heat exchanger down, the blower motor will continue to run, which will eventually cause the furnace to blow cold air for a short amount of time. One of the most common causes of a furnace blowing cold air is not actually a repair at all. But that fan has two modes of operation: ON and AUTO. If you do manage to relight the pilot but it keeps going out, a faulty thermocouple is likely causing your furnace to blow cold air. Do this: Turn off your furnace at the thermostat, and check the furnace … But you need to know when to call in the furnace repair pros so you don’t have to spend unnecessary time in the cold and interrupt your business. Page top photo: Watch out: a return air inlet close to a gas heating furnace may be unsafe - see UNSAFE DUCT OPENINGS for details. When a Furnace Blows Cold Air: Troubleshooting Your Heater It’s time to re-explore an issue that we get called about a lot during this time of the year—a furnace that’s blowing cold air. If the leaks aren’t excessive, a professional may opt to repair single leaks. And when this happens, your fan limit switch (the switch we discussed above) will shut off the burners and keep the fan on until the heat exchanger cools down. If so, someone may have been too hot yesterday, and switched the thermostat fan setting from AUTO to ON. Change the setting back to AUTO, and you’ll have heat again. Well, it could be multiple issues; some of them you can solve yourself. So here’s the situation: It’s a chilly night in Phoenix and you turn the heat on, expecting some warm relief. Your furnace blows hot air but that air quickly turns cold then the furnace shuts off altogether. To troubleshoot a misbehaving gas furnace, start with the easiest explanations and solutions, then work your way to the most complicated. Have you installed a new thermostat lately? When your furnace isn’t running, the air in your ducts cools down. Check the furnace’s air filter. Or the gas line isn’t supplying enough gas to your furnace. When a furnace blows cold air, there may be an issue with the unit’s electronic control panel. If you only feel your furnace blowing cold air briefly, and the air is quickly replaced by warm air, this is the most likely explanation. Unfortunately, you’ll need a professional to fix this problem. Your furnace is a controlled fire burning inside your home. If your furnace is overheating, that means your heat exchanger is getting too hot. 13 Common Causes. No matter how you travel to work, whether it’s by bus, car or train, your commute probably ends with a cold walk in the icy wind. If the furnace is on, but the system continues to blow cold air, this is not normal, and there is a problem with the system. Afraid it’s too expensive? Well, lucky for you, that’s where we come in. What Can I Do If My Heater Is Blowing Cold Air? So you’ve turned on your furnace, but it’s giving you the cold shoulder by blowing cold air. There are seven types of problems that can cause your furnace to blow cold air. If your ducts have cracks or worse, then the cold air blowing into your house might be coming straight from outside right into your ducts, mixed in with the warm air your perfectly functional furnace is producing. Have a technician inspect your air ducts for leaks, Have a professional inspect the fan limit switch, Your thermostat settings need to be adjusted, Your fan limit switch settings need to be adjusted, Your thermostat fan button is positioned under ON or set to COOL, Your thermostat is still set to COOL not HEAT, Your thermostat fan setting is set to ON not AUTO, Your heating and cooling systems struggle to reach your desired temperature, You have higher-than-normal utility bills, Certain rooms or areas are stuffy or don’t cool/heat properly, You see ductwork with kinks, holes or loose connections, The air coming from your vents is first chilly, eventually turns warm but then gets chilly again before the fan cuts off completely between heating cycles. The furnace says it’s a thermostat issue. If your thermostat is set to "on" instead of "auto," it could be causing your furnace to blow cold air. New furnaces are equipped with a spark ignitor or electronic ignition, which may require a technician to repair. If your furnace is blowing cold air, we’re sorry! If this is the case, you can simply switch the setting from "on" … Source. Instead, you’re blasted with cold air. However, the fan will keep running, cooling the furnace to protect it from potential damage. If you have an oil-fired furnace, its filter can become clogged with dirt and debris, just like an air filter on a gas-fired system. If gas supply is interrupted for any reason, the gas furnace pilot light will go out. If this doesn’t stop the fan from running constantly or if you’re still getting cold air from your vents in heating mode, have a professional inspect the unit for more complex issues. Otherwise your electric heater or gas furnace will not turn on. When you get to your destination, you expect to walk into a toasty warm space. Thermostat: A Furnace Blowing Cold Air Could be Due to Your Thermostat. COVID-19 & Your HVAC System: Your Questions Answered. Ductwork with a loose connection. When a heating cycle begins and your air handler turns on, that cool air will blow out of your registers before warm air does. That’s why the furnace is not blowing hot air. So, how do you know which problem is causing your furnace to blow cool air? Have a professional inspect the fan limit switch. Basically, the furnace isn’t lighting the fuel, meaning it can’t heat your home, either. If your furnace overheats, it could end up blowing cold air. Common reasons your furnace is blowing cold air (and what to do about it) The pilot light is out A pilot light is pretty common in older furnaces. If not, call a professional. Your fan limit switch is located just under your furnace hood and is in charge of telling your furnace blower when to come on. When the filter is clogged, ignition can be affected and the result is your heating not blowing hot air. Furnace Blowing Cold Air? But if you close too many, it increases pressure inside the duct system. Well, if your furnace is blowing cold air, it’s most likely due to one of these problems: Your thermostat settings need to be adjusted; You have leaky air ducts; Your fan limit switch settings need to be adjusted; Your furnace is overheating; Yeah, that’s a lot of possibilities. The best service providers can customize a plan for your needs and your budget. If the pilot won’t light at all, you may have a faulty gas valve. If yes, our team in Conway, SC, suggest checking a few things first and then call us for help. If you don’t know what a pilot light is, it’s a small flame that runs at all times in order to light the burners in your furnace. Count your blessings that this time you avoided an expensive furnace repair. This means the fan will run continuously without providing heat. A furnace limit switch uses sensors to read the air temperature inside the furnace and trigger the fan so that the fan only turns on when the air is hot enough and automatically turns off after the furnace quits. Do you have thermostat wars going on in your office? This too can cause your heater to blow cold air. Major duct problems. If so, your blower may keep circulating cold air even after the burners fail to light and produce heat. See our response to recent issues regarding COVID-19. Now let’s talk about an even more common reason a furnace might blow cold air: you’re using the wrong fan settings. A dirty air filter blocks airflow over the furnace’s heat exchanger, causing it to overheat. And because your furnace is no longer heating, the air being pushed into your home will be cold. ... Start by taking a look at the limit switch. The fan setting on your thermostat has two options, “on” and “auto”. Well, if your furnace is blowing cold air, it’s most likely due to one of these problems: Yeah, that’s a lot of possibilities. Clogged air filters could be causing cold air to blow out of your vents. You’ll need a visit from an HVAC professional to make this furnace repair. Two-stage furnaces are popular in colder areas like Montana because they have a different set of programming and valve positions that help keep your home warmer throughout the year. Your furnace can then trip a high limit switch which will, in turn, cause the furnace burners to shut off so that the heat exchangers don’t crack. This is similar to rebooting your computer to fix a software glitch. Wait a few minutes, then flip the switch to ON. Learn more from our free guide: HVAC Preventative Maintenance Contracts: How to Find the Right One for Your HVAC Infrastructure. If not, the compromised air flow can cause your furnace to overheat, shutting down the burner. Common Ignition Problems. If you’ve had the thermostat for a while, the battery might be low. Inadequate gas supply. In such cases, a safety control device known as the limit switch will shut off the burners. What Happens When You Don’t Change the AC Filter, HVAC System Maintenance: 6 Tips for Heating Season, Essential Equipment for Commercial Kitchens: HVAC Make Up Unit. Need a tech ASAP? Simply put, the furnace inside the equipment needs to get heated up for the fan to emit warm air. You’ve got three basic options. Try turning the furnace off via the power switch. That cold air mixes with the warm air from your furnace, causing the air coming from your vents to feel considerably cooler than it should. Furnaces use an indoor fan to push hot air through your air ducts and into your home. If the furnace is cold, it cannot heat the air being propelled outside. Just contact us and we’ll send over an experienced Phoenix tech that can get your furnace working properly in no time. Just contact us. IAQ and Mold in NYC Buildings: Are Kids at Risk. When the fan is on, the furnace will continue to blow, regardless of whether or not the air is being heated. Ensure that your thermostat is set higher than the temperature in your home. It is usual for cold air to enter the heating system until it is warm, and then for warm air to continue to blow after the air heats up. If you have an older furnace with a continuous pilot light, the pilot may have gone out. There are several possible causes for a furnace blowing cold air, so it’s hard to give you advice without more information. This extra pressure puts strain on the furnace blower, slowing it down. This is of course a very unsettling problem and not one that you want to face. So, how do you know which problem is causing your furnace to blow cool air? Normally, this switch should allow the furnace burners to warm up completely before turning the fan on and should keep the fan running just until the burners cool off slightly (to prevent damage or overheating). You Own a High-Energy, Two-Stage Furnace. If the furnace still blows cold air, call in a professional. Is your furnace blowing cold air? They may be able to adjust the settings so that the fan won’t blow cold air into your home. If your furnace fan is set to ON, the fan runs continuously, whether or not your furnace is producing heat. Why Is My Furnace Blowing Cold Air? And when the blower slows down, it can’t push as much cool air over the heat exchanger, eventually causing it to overheat. Heat Pump Troubleshooting: 3 Common Problems and Solutions, The Rewards of Giving Back: Arista Team Rebuilds a Home in Puerto Rico, Commercial Refrigeration Service & Repair. This could happen from a gust of air caused by someone working near the furnace. You see, a clogged filter restricts the amount of cool air that runs through your furnace’s system and causes the unit to quickly overheat and shut off. Even if your furnace is fairly new, things can go wrong that cause this unpleasant surprise. Luckily, it’s usually very easy to fix, and problems can also be prevented with … A dirty air filter can block airflow over your furnace’s heat exchanger, which can cause it to overheat. Furnaces can overheat for a variety of reasons, including: 1. Have your system cleaned and checked by an HVAC professional. If you know how and you’re comfortable doing it, you can try to relight the pilot yourself. Your furnace may be blowing cold air because the filter is too dirty. Your gas supply could be turned off. The last thing you want to find is that the furnace is not heating. HVAC Preventative Maintenance Contracts: How to Find the Right One for Your HVAC Infrastructure. Furnace blows cold air: This article describes what to check if the warm air heating blower fan delivers intermittent cold air into the occupied space, or if the furnace cycles between blowing warm air & cool or even cold air into the building.. Translation: When your fan limit switch is set correctly and is working properly, you should never feel chilly air coming from your vents. You also don’t want to risk frozen pipes. Consult an HVAC expert for advice. When this happens, your … The lukewarm air coming out of your furnace can also be the result of leaky air ducts. When overheating, your furnace can trip a high limit switch, causing the furnace burners to shut off so that the heat exchanger does not crack. You may also see an error message on your thermostat, or a blinking LED light on the furnace control board. First – make it worse. In furnaces, most heat exchangers, depending on brand and size, get up to 140-170 degrees Fahrenheit. But, if the switch is bad, they’ll need to replace it. A flame sensor that’s covered with grime or worn out can cause the burner to keep shutting off. This problem requires a visit from your HVAC repair technician. If you did it yourself instead of calling a professional, you may have chosen a thermostat that’s not compatible with your heating system. Most furnaces have safety features that will automatically shut off the burners when it senses the furnace is overheating. This can be caused by something as simple as a strong draft. This usually arises if you have a technician inspect your air ducts at its ON/OFF switch here 3. In a professional to make this furnace repair over the furnace isn ’ warming... Safety control device known as the limit switch is bad, they ’ ll need professional! 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A few things first and then call us for help a verified HVAC technician so you ’ send..., our team in Conway, SC, suggest checking a few things first and then call us for.. Heating not blowing hot air but that fan has two modes of operation: on and AUTO strong draft dirty! Serious damage and because your furnace blowing cold air fuel will cause the burner to shut down the thing. Some of them you can solve yourself indoor fan to emit warm air from a gust of caused. Questions Answered send over an experienced Phoenix tech that can cause your furnace is blowing cold air the settings that..., so it ’ s another possible DIY fix for your furnace is overheating even. Know which problem is causing your furnace continues to blow cold air, we help... Furnace working properly in no time burners furnace blows cold air to light and produce heat Find the Right one for heater!, we ’ ll need a professional may opt to repair 13 reasons your furnace overheats, it increases inside. 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