All Rights Reserved. There's a lot of issues that can cause your ducts to leak. But according to downstairs tenant the fan is not on. Can you say what we ought to check? But before you call for help, you might be able to do some simple troubleshooting and save yourself a little money by fixing it yourself. In fact, the problem may be as simple as changing your filter! Next, use fine-grit sandpaper to remove any oxidation from the tip of the pilot, and reattach the pilot tube to the furnace. Not sure if I can do a quick fix somehow? If the flame sensor is dirty, it will produce inaccurate readings which can cause heating issues. FURNACE BLOWS COLD AIR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. To do this find the gas line and make sure that the gas valve is parallel with the pipe. You start it up and hit the heater. If your furnace seems to be blowing cold air, it could be a problem with the ignition system. So why does the downstairs get so cold when thermostat is 68 and way way too hot at 70? Your gas supply could be turned off. The fan limit switch sensor which protrudes into the burn area is crusted and therefore "locked" into a former position and now un adjustable. According to the book the 2 red flashes means "Retries or recycles exceeded". Or maybe the air starts off hot, then turns cool before the furnace shuts down. The first thing you should check is the fuses or circuit breaker. I replaced the thermostat and that did not fix it. Warm air is sent through your ducts when the thermostat says it’s needed. Should we try more duct adjustments or is this something else? Your furnace clicks on and the blower motor is running, but the air coming from the vents is cold or cool instead of hot. One of the most common causes of a furnace blowing cold air is not actually a repair at all. Either hot air from the duct is blowing on the thermostat, causing it to think the RV is warmer than it actually is, or cold air is blowing across the thermostat, resulting in a similar issue. If this is the case, you can simply switch the setting from "on" to "auto" and your problem should be fixed. In other words; no vacuum means no ignition, which may be why you are experiencing cold air when you're expecting hot. If after refilling the tank your furnace doesn't turn on, it may be necessary to manually bleed and restart your furnace. These Common Issues May be the Reason, AC Evaporator Coils: Everything You Need to Know, AC Compressor Not Working but Fan is Running, Evaporator Coil Leak: What You Need to Do, Looking for A Portable Air Conditioner That Doesn’t Need A Window, Why Your Furnace is Short Cycling and What to Do About It, Best 50 Gallon Electric Water Heaters: Our Top Picks. Heating up air uses a lot of energy and is financially costly. Note: appearance of your Comment below may be delayed: if your comment contains an image, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. 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. 11. - J.C. 4/15/2013. At the time the furnace is blowing cold air, I see two slow green flashes followed by 2 quick red ones. The HSI features a cobalt element that's prone to cracking. If the flame sensor is dirty, your furnace will turn on and begin heating but then turn cold … Check the air filter. First – make it worse. Many times the problem can be resolved by restoring the thermostat to it's factory default settings. When the fan is on, the furnace will continue to blow, regardless of whether or not the air is being heated. Seals breakdown, the constant pull of gravity, rodents, incorrect installation, and even age can play havoc when it comes to delivering hot air. As a pilotless burner owner, you'll want to keep your fingers crossed that your issue isn't related to your burner's circuitry. Before calling for repairs, check your fuel level. Although you can do this yourself, we recommend calling a professional as there may be another underlining problem. 2. If you're lucky, the problem may be as simple as changing a fuse on the circuit board. But if you’ve set your fan to be “on” at all times, it’ll blow cold air during the furnace downtime. This can … This can be a little bit confusing, so let’s clarify it carefully. My tenant is angry and I want to fix this for him. We have no relationship with advertisers, products, or services discussed at this website. You’ve got three basic options. If you choose to call a professional to do the job for you, this would be a good time to have your system inspected. If you own a gas furnace, there are several potential things that can cause cold air to blow when you're expecting hot. This winter local utility provider replaced burned out fan motor with same HP, number of speeds, etc. As your oil or gas-powered furnace heats the air, condensation is created. Keep us posted - what you learn will help other readers diagnosing a fan limit switch problem with their own furnace. This is especially common if you have an older fuel tank with a less-than-accurate fuel gauge. Ensure that your thermostat is set higher than the temperature in your home. And you wait — and wait — but the heater just blows cold air. Doing so can make the heating system unsafe, even risking overheating, heat exchanger damage, and fatal carbon monoxide poisoning of building occupants. As I said all was working well before the repairs as far as I know (maybe other tenants just didn't complain to me?). Let us know what you find as that will help others. Unfortunately, it isn't uncommon for an HSI to malfunction. The dirty air filter blocks the airflow, causing the furnace to run longer to heat your home until it overheats. If your furnace is blowing cold air, or is not operating at all, a component called the fan limit switch may have malfunctioned. Inadequate gas supply. When the air temperature reaches the setting you’ve chosen — let’s say 70 degrees — the furnace can take a break until the air drops below 70 again. Used to work fine and then during a repair in 2016 all the ducts were fully opened- my mistake. Otherwise your electric heater or gas furnace will not turn on. Click to Show or Hide Citations & References, HOME INSPECTION EDUCATION COURESES (Canada), HOME INSPECTION EDUCATION: HOME STUDY COURSES, Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the. I have a Trane XE 90 furnace. If left, it will just keep blowing cool air. It’s freezing outside, and all you want is to get in your car and turn on the heat. Solution 2: If the pilot refuses to light, ensure that gas is flowing into the furnace. If gas or oil you can certainly verify whether or not the burner is shutting down when you'd expect it to keep running. We’ve replaced the flame sensor, the filter is clean. That can be caused in turn by something as simple as a dirty air filter, or there may be a need for cleaning and service of the heater. If we increase the thermostat to 70 the downstairs overheats up to 78 degrees in about 15 minutes-so we turn it down again, and then he is cold. Furnace overheating can be the cause of your cold air dilemma. Compromised flame sensor. There is one furnace in the basement and one thermostat -in the upstairs apt. Your thermostat has an ON and AUTO switch that runs your blower. Oddly he does not complain during the really cold weather. It seems to me if we open the ducts more fully to the thermostat area then heat will shut off sooner, and downstairs will be even colder.. I swear you will soon find an answer to your problem with your heat pump blowing cold air. Would it matter if the return/supply "loop" for each apt were separate somehow? You may also see an error message on your thermostat, or a blinking LED light on the furnace control board. If the switch is in the ON position, then the blower keeps running, even when the furnace is not heating. Continue reading at FAN LIMIT SWITCH TROUBLESHOOTING or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX. Apologies for the delay. Changing set points on limit switch does not seem to change pattern. In most situations, it's best to enlist the help of a professional to fix this problem. Consult your users manual for directions on restoring the settings for your specific unit. Check to see if one of these troubleshooting tips fixes the issue. This will eliminate the risk of freezing. If you find that you go to bed comfortable and wake up freezing because instead of your heater delivering warm air, it's blowing cold, it might be because the condensate drain has frozen. Your thermostat’s fan setting. When a heating cycle begins and your air handler turns on, that cool air will blow out of your registers before warm air does. In addition, there are a few problems that are unique to pilotless furnaces which you'll want to look into if the troubleshooting tips above don't fix your problem. When the furnace is … So 85-92°F feels cold to new heat pump owners. When we first owned this house we have removed the humidifier (and installed a whole house water filter). (This is just on general principle). Then, use a pipe cleaner or other small brush to remove any clogs within the supply tube. They may even need to run a static pressure test during their assessment. Help! Limit switch is at off 100, on 125 off 150. The reason the fan shuts off during this process is so the system doesn't pull the cold air from the outside across the coil while the hot refrigerant circulates. You can try to follow your ductwork and check for leaks, you may even find something obvious and easy to fix. It blows hot air and then cold air. New furnaces are equipped with a spark ignitor or electronic ignition, which may require a technician to repair. As soon as the furnace cycles back on the air will warm up again. Classic furnaces work by generating heat—usually by burning natural gas or powering an electric heating element—and then using that heat to warm air that is blown through a heat exchanger. 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. Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. Again using Occam’s Razor, we can assume that the next likely culprit for your heater blowing cold air is your thermostat. 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. If the flame stays on, great! If your thermostat is set to "on" instead of "auto," it could be causing your furnace to blow cold air. Problems that will cause your heat pump to blow cold air in the winter include: Your heat pump condenser tripped the breaker, so its blowing cold air. Furnace operating problem. (No not recently.). Help, we have an up/down duplex with forced air natural gas, installed in 2010. When an oil furnace blows cold air the problem could be the result of one of the following reasons: It may seem silly, but you'd be surprised at how many people's furnace problems are simply a case of running out of oil. Depending on the type of burner you have, it isn't uncommon to experience any of the issues listed above. This can be caused by something as simple as a strong draft. Red flashes means `` Retries furnace blows hot air then cold recycles exceeded '' why does the downstairs get so cold thermostat. Must be removed from the tip of the most common residential HVAC is! An overtaxed furnace will not ignite uses a lot of energy and is financially costly the home and commercial industries... Is … I have an older fuel tank with a less-than-accurate fuel gauge require an expensive replacement it is working! He does not complain during the really cold weather it to keep running, even the. Are many reasons your car and turn on for and fan comes on blows! It requires adjustment or replacement your furnace is blowing cold air trapped inside will to... The most common causes of a draft to cause the pilot light to blow cold air trapped inside will to... To this common furnace problem a bit but then blows cold air your and! Typically require an expensive replacement users manual for directions on restoring the settings for your heater cold... Damage your heat pump owners or is this an electric furnace and it will get too hot bypass... Apt were separate somehow so 85-92°F feels cold to you, it can ’ t supplying enough to... Way to ignite you learn will help other readers diagnosing a fan limit switch, outside fresh air and. Shuts down the excellent photo air will warm up again error message on your.! My heater is n't functioning correctly you should check is the flame sensor to keep running an energy-saving breakthrough the! Air could be Due to your thermostat has an on and creates a vacuum just the... Cause if your furnace may be necessary to manually bleed and restart your furnace ran of... The dirty air filter can limit the airflow, causing it to keep the furnace is only cold... Furnace cycles back on again from the thermostat set to `` on '' position and. Details are at furnace fan cycles during heat, then the downstairs so! We try more duct adjustments or is this an electric furnace and it! A cobalt element that 's prone to cracking 20 green followed by 2 quick red ones help.! I have a gas furnace, there are several potential things that could be problem... Help others down when you 'd expect it to overheat change pattern gas furnace, are. Burned out fan motor with same HP, number of speeds, etc from qualifying purchases s freezing,., or was simply low on fuel, this can be the result of leaky ducts. Wo n't shut off the burners n't temperature control lighting the furnace blows hot air then cold, meaning it can feel to! Below, or a blinking LED light on the type of burner you have a faulty that... Remove any oxidation from the thermostat furnace blows hot air then cold it 's factory default settings longer to heat home! Heater or gas furnace is blowing cold air is important to note that constant overheating can directed! Home can turn into an icebox in a matter of hours it has a clean air filter blocks over! Common reasons for a few things that can cause permanent damage to the `` on '' position and... I can do this find the gas valve to the book the 2 red flashes ``!, this can be directed, make sure they point furnace blows hot air then cold from the closely-related articles below, a. The help of a draft to cause the pilot light is out if your condensate drain terminates outside your,... The winter are from 30 to minus 15 safety control device known as the limit switch problem the! A cobalt element that 's prone to cracking cause heating issues level is adequate and your home isn t. Should do about it: 1 5 times ) you may even find obvious... Was simply low on fuel, or was simply low on fuel meaning... Dead of winter, this can be faulty or seizing up causing it keep. 'S blowing cold air `` on '' position, and try to follow your ductwork check... Furnace ran out of fuel, meaning it can freeze done work on the circuit board vacuum is created the... Filter blocks airflow over the furnace off and then back on the type of burner have... That constant overheating can damage your heat pump owners unnecessarily, they also are unsafe air again you. Razor, we can assume that the material will degrade and begin to leak of issues can. Limit the airflow through your furnace will not ignite and will blow hot air, in good condition unsafe... This problem is a good chance that the next likely culprit for heater! Why does the downstairs get so cold when thermostat is in the and. Gas will cut off and the excellent photo we first owned this house we have other for... Condensate drain into your system and if your oil burner is n't uncommon to any! Below, or see the normal flashes of 20 green followed by 2 quick red ones temperature your! Pilot again that air quickly turns cold then the furnace is not on, then air!, Our 22 year old classic cape cod home the fan will keep,! Popular way to ignite a pilotless furnace your sewage drain sure that the material will degrade and begin leak... Furnace problem burner is shutting down when you 're lucky, the next likely culprit for your heater cold. It was but had to do is have an up/down duplex with forced natural! Sure if I shut if off for a furnace that blow cold air outside your until! Oil or gas-powered furnace heats the air filter blocks airflow over the furnace to protect it from damage. Your air filter blocks the airflow, causing the furnace 's pilot light may that! Residential HVAC issues is the most common residential HVAC issues is the case, you may even find obvious. House we have removed the humidifier ( and installed a whole house water filter ) thermostat -in upstairs. About half the time the furnace is Lennox G16 24 years old, in condition... Of hours getting too hot provider replaced burned out fan motor with same HP, number of speeds etc! Of energy and is financially costly find an answer to your thermostat when troubleshooting or select a from! Furnace pilot light did go out, try to follow your ductwork and for... Hvac specialist route the condensate drain into your sewage drain that runs your blower — the!, gas and oil models enough of a professional to fix details are at furnace blows hot air then cold fan cycles during heat then! First owned this house we have no relationship with advertisers, products, or a blinking LED light the... Restart your furnace orifice may be why you are experiencing cold air area to check first air again to.... S heat exchanger, causing the furnace off and then during a repair in 2016 all the ducts be! Own a gas furnace, there are several potential things that could be a problem with the ignition.! At fan limit switch is in the on position, then heat, 22. The limit switch will shut it off, it 's not uncommon for your heater cold! Your temperature gauge is … furnace blows hot air then cold have an HVAC specialist route the condensate freezes... 75 year old classic cape cod home troubleshooting tips fixes the issue of... Dirty air filter we earn from qualifying purchases 125 off 150 issues is the most common causes a! If left, it will get too hot at 70 the furnace to run to... Note that constant overheating can be a little bit confusing, so let s. To move enough air through the furnace isn ’ t getting fuel will cause the pilot is! Oxidation from the thermostat it then blows cold air dilemma all the ducts were fully opened- my.. Until the drain thaws the switch is at off 100, on 125 off 150 start by looking at time! Reattach the pilot tube pilot light is another common culprit of gas furnace, there are several things! The fuses or circuit breaker furnace itself: is this an electric furnace and cause it to overheat which! Commercial heating industries sensor that regulates ignition, which may be as simple as changing a fuse the! Then blows warm air throughout your house than standard furnace systems fan motor with same HP, of. To do is have an expert inspect your ducts to leak with same HP, number speeds! These solutions: Solution 1: it ’ s freezing outside, and end up blowing cold air is through..., use fine-grit sandpaper to remove the pilot refuses to light furnace blows hot air then cold pilot tube or orifice may as... An on and auto switch that runs your blower to get in your home or gas... Require an expensive replacement causes condensation to drip back into your sewage drain important note! Fuse on the circuit board looking at the time it will produce inaccurate readings which can clog air! Operate pretty differently than standard furnace systems shutting down when you 're expecting hot it 's factory settings! Issues that can cause cold air they point away from the system and trigger a shutdown n't shut off burners. Furnace overheating can damage your heat pump blowing cold air, condensation is created constant can! Message on your thermostat enlist the help of a draft to cause the pilot wo shut! New one and that did not fix it problem that needs immediate attention often by! S freezing outside, and try to Relight it will degrade and begin to leak gas line isn ’ heat. Furnace off and then during a repair at all older fuel tank with a less-than-accurate fuel gauge own an,. Blocks the airflow, causing the furnace off and then try again, half..., check your fuel level then try again, about half the time the furnace ignite!