It has always done this. I don't know what's happening with your heating system but I can, from your note make a few diagnostic suggestions: Watch out: you are quite right not to force the set point adjustments on a fan limit switch. You’ve got three basic options. The oil from your fingers can cause permanent damage to the part. Compromised flame sensor. 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. 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. As an Amazon Associate we earn from qualifying purchases. 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. Not sure if I can do a quick fix somehow? The lukewarm air coming out of your furnace can also be the result of leaky air ducts. I like Dan Holohan's expression "Keep your hands in your pockets" - my mom used to make me sitOn my own hands. The pilot light is another common culprit of gas furnace problems. We have no relationship with advertisers, products, or services discussed at this website. If we close them the heat will stay on longer and it will get too hot. According to the book the 2 red flashes means "Retries or recycles exceeded". This winter local utility provider replaced burned out fan motor with same HP, number of speeds, etc. Apologies for the delay. The furnace fan limit switch assembly is intended to be adjusted within a safe range by the heating service tech by moving the stops, but if you bend something the switch is damaged and unsafe, and if you set the switch incorrectly (for example fan coming on too late or turning off too early, or setting the upper limit too high) there is risk of overheating the heat exchanger, cracking it, risking fatal carbon monoxide poisoning at worst, or perhaps a costly heat exchanger or furnace replacement job. 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. If it stays lit, you should be back in business. As your oil or gas-powered furnace heats the air, condensation is created. We’ve replaced the flame sensor, the filter is clean. Also, if your oil burner isn't functioning correctly you should check for a clogged filter. InspectAPedia tolerates no conflicts of interest. Discussed here: what to check if the forced warm air furnace blows cold air out of the supply registers, or cycles between blowing warm air & cold air. The flame sensor itself is relatively easy to clean, but many homeowners are uncomforable working on their furnaces. If your furnace is blowing cold air, or is not operating at all, a component called the fan limit switch may have malfunctioned. Would it matter if the return/supply "loop" for each apt were separate somehow? If the flame sensor is dirty, it will produce inaccurate readings which can cause heating issues. 1. Oddly he does not complain during the really cold weather. At the time the furnace is blowing cold air, I see two slow green flashes followed by 2 quick red ones. This is especially common if you have an older fuel tank with a less-than-accurate fuel gauge. 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. Solution 2: If the pilot refuses to light, ensure that gas is flowing into the furnace. 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 cleaning the pilot tube and ignition element doesn't solve the problem, and you continue to lose your pilot, the thermocouple may be defective. The furnace will be more likely to pull in sediment from the tank, which can clog your air filter. Heat pumps are a different beast altogether. Once every few days, the furnace will kick on as normal, send out heat, but after a few minutes we’ll notice that it’s blowing cool air. These components typically have a 3 to 5 year service life, so it's a good idea to keep a spare on hand for when it inevitably needs to be replaced. If the flame sensor is dirty, it will produce inaccurate readings which can cause heating issues. Maybe the fan is malfunctioning. An HSI or Hot Surface Ignitor is the most popular way to ignite a pilotless furnace. When I turn the furnace off and then back on again from the thermostat it then blows warm air again. The HSI features a cobalt element that's prone to cracking. It has always done this. Gas furnaces produce air that is 130-140°F range. Perhaps your temperature gauge is … The fan blows fine. If this is the case, you can simply switch the setting from "on" to "auto" and your problem should be fixed. There's a lot of issues that can cause your ducts to leak. Limit switch is at off 100, on 125 off 150. The fan limit switch sensor which protrudes into the burn area is crusted and therefore "locked" into a former position and now un adjustable. And you wait — and wait — but the heater just blows cold air. Heating up air uses a lot of energy and is financially costly. What do you think? Although you can do this yourself, we recommend calling a professional as there may be another underlining problem. We have owned home 12 years. Check the air filter. Check that the air filter is clean and that the ductwork is not obstructed. They are available in electric, gas and oil models. If after refilling the tank your furnace doesn't turn on, it may be necessary to manually bleed and restart your furnace. It seems like something else besides ducts is the problem. Let us know what you find as that will help others. The flame sensor itself is relatively easy to clean, but many homeowners are uncomforable working on their furnaces. It's blowing warm air at the moment. by (mod) - furnace blows cold air - what to check first. Copyright 2021 Think Tank Home. This “hot then cold air” sequence happens over and over and your home isn’t warming up. When your furnace is blowing cold air your warm and inviting home can turn into an icebox in a matter of hours! This can be caused by something as simple as a strong draft. Turn the gas valve to the "on" position, and try to light the pilot again. FURNACE BLOWS COLD AIR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. Two different people worked on the 2016 repair. Ensure that your thermostat is set higher than the temperature in your home. I have a Trane XE 90 furnace. Your furnace may be blowing cold air because the filter is too dirty. It willheat for a bit but then blows cold air. We live in central NY-temps during the winter are from 30 to minus 15. After checking that your fuel level is adequate and your filter is clean, the next area to check is the flame sensor. In some buildings we like to run the blower fan continuously for more even heat distribution and improved air filtration - improvements to building indoor air quality. 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. When heat called for and fan comes on it blows cold air, then heat, then cold, then off. But if you’ve set your fan to be “on” at all times, it’ll blow cold air during the furnace downtime. Use a wrench or pliers to remove the pilot tube. When we first owned this house we have removed the humidifier (and installed a whole house water filter). Your furnace blows hot air but that air quickly turns cold then the furnace shuts off altogether. In most situations, it's best to enlist the help of a professional to fix this problem. This will eliminate the risk of freezing. With that said, even if you recently changed your filter you should check it again. But you might want to consider calling a professional HVAC service who has the knowledge, tools and experience to find and repair the problem. Continue reading at FAN LIMIT SWITCH TROUBLESHOOTING or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX. Since then the downstairs apartment gets cold (like 62-64) with the thermostat set to 68. Pilotless ignition furnaces use a flame sensor to keep the furnace burning once it starts. If the flame sensor is dirty, your furnace will turn on and begin heating but then turn cold … Or maybe the air starts off hot, then turns cool before the furnace shuts down. Furnace operating problem. 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. 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.. Many times the problem can be resolved by restoring the thermostat to it's factory default settings. Change the air filter If your furnace overheats, it could end up blowing cold air. If the flame stays on, great! If you own an electric furnace and it's blowing cold air there's a few things that could be causing the problem. If you suspect a dirty air filter, change the filter, press the reset button (if your furnace has one), and see if your furnace begins to emit heated air. Check the following two switches to make sure that the furnace blower fan is not simply set to run continuously: If you need to introduce outdoor air into a building for air quality reasons, consider an air to air heat exchange system to save on heating costs. Thermostat: A Furnace Blowing Cold Air Could be Due to Your Thermostat. First – make it worse. The first thing you should check is the fuses or circuit breaker. Again using Occam’s Razor, we can assume that the next likely culprit for your heater blowing cold air is your thermostat. You start it up and hit the heater. 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. In a furnace, the heat being produced and blowing into your home starts out at upwards of 110 or more degrees, often much higher than that. This can be a little bit confusing, so let’s clarify it carefully. I don't remember what it was but had to do with wiring. If the ducts can be directed, make sure they point away from the thermostat. 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. At my request a few days ago the tenant with thermostat set the fan to be ON all the time -and assures me it's still on. If you're lucky, the problem may be as simple as changing a fuse on the circuit board. 2. One of the most common causes of a furnace blowing cold air is not actually a repair at all. Check to see if one of these troubleshooting tips fixes the issue. it resets and works properly. Recent information. Is your furnace not blowing hot air? Two story 75 year old classic cape cod home. 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. Help! I swear you will soon find an answer to your problem with your heat pump blowing cold air. A dirty furnace filter is the root cause of many problems. Before calling for repairs, check your fuel level. They may even need to run a static pressure test during their assessment. In such cases, a safety control device known as the limit switch will shut off the burners. Can you say what we ought to check? If your thermostat is set to "on" instead of "auto," it could be causing your furnace to blow cold air. 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. Warm air is sent through your ducts when the thermostat says it’s needed. Changing set points on limit switch does not seem to change pattern. Thanks for the interesting question and the excellent photo. Page top photo: Watch out: a return air inlet close to a gas heating furnace may be unsafe - see UNSAFE DUCT OPENINGS for details. It’s freezing outside, and all you want is to get in your car and turn on the heat. We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. New furnaces are equipped with a spark ignitor or electronic ignition, which may require a technician to repair. Furnace overheating can be the cause of your cold air dilemma. If this is the case, you'll first want to turn the gas valve that supplies the pilot light off. If you have a gas furnace, a lack of fuel will cause the pilot light to go out. To do this find the gas line and make sure that the gas valve is parallel with the pipe. So 85-92°F feels cold to new heat pump owners. The Flame Sensor is Dirty. As I said all was working well before the repairs as far as I know (maybe other tenants just didn't complain to me?). All Rights Reserved. Changing set points on limit switch does not seem to change pattern. Have an expert inspect your ducts along with the furnace. When a heating cycle begins and your air handler turns on, that cool air will blow out of your registers before warm air does. A dirty furnace filter can limit the airflow through your furnace and cause it to overheat, which will shut it off automatically. However, the fan will keep running, cooling the furnace to protect it from potential damage. (No not recently.). 11. Used to work fine and then during a repair in 2016 all the ducts were fully opened- my mistake. More diagnostic details are at FURNACE FAN CYCLES DURING HEAT, Our 22 year old furnace just started having intermittent problems. 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. I have a York Diamond 80 furnace. This can … (has AC). If your furnace seems to be blowing cold air, it could be a problem with the ignition system. If your gas furnace is blowing cold air and won't shut off, it could be related to a blown pilot light. 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. It blows hot air and then cold air. 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 might be suprised to learn that one of the most common residential HVAC issues is the thermostat. Changing your filter is a good starting point, but if the problem persists we have other options for you to troubleshoot. Seals breakdown, the constant pull of gravity, rodents, incorrect installation, and even age can play havoc when it comes to delivering hot air. Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly. You may also see an error message on your thermostat, or a blinking LED light on the furnace control board. I don't know if they are-just thought of it. Now about that pesky fan limit control, you could. But if it doesn't light, or it won't stay lit, you'll want to check that gas is flowing to the pilot. If this is the case, someone walking by the burner could generate enough of a draft to cause the pilot to go out. Once the vacuum is created, the vacuum switch sends a signal for the furnace to ignite. 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. Is it possible one made an adjustment (or work around) that he should not have? When this is the case there's a good chance that the material will degrade and begin to leak. I replaced the thermostat and that did not fix it. Explanation: If your furnace is overheating, that means your heat exchanger is getting too hot. Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. If not, then keep reading. Ductwork is often installed in areas such as attics, garages or crawl spaces where there isn't temperature control. If the gas is on, but the pilot won't light or stay lit, the pilot tube or orifice may be dirty. What Can I Do If My Heater Is Blowing Cold Air? The dirty air filter blocks the airflow, causing the furnace to run longer to heat your home until it overheats. Limit switch is at off 100, on 125 off 150. Your body temperature is around 98.6°F (everyone’s body temperature is slightly different, but that’s the average). A furnace that isn’t getting fuel will not ignite and will blow only cold air. Leaky ductwork can cause serious issues for your heating system. Depending on the type of burner you have, it isn't uncommon to experience any of the issues listed above. When the condensate drain freezes, it causes condensation to drip back into your system and trigger a shutdown. If your gas company has recently done work on the gas lines, it's not uncommon for your pilot light to blow out. An overtaxed furnace will often overheat and malfunction, and end up blowing cold air. Your furnace clicks on and the blower motor is running, but the air coming from the vents is cold or cool instead of hot. But still the same issue. Since heat pumps produce air that’s below that, it can feel cold to you. The Heat Pump Condensing Unit. The best thing to do is have an HVAC specialist route the condensate drain into your sewage drain. By switching the thermostat to “auto,” the fan will only blow when the furnace is heating the air. I would start by looking at the furnace itself: is this an electric, gas or oil unit? That may be a quick and easy fix. Your thermostat’s fan setting. Unfortunately, more complex issues in this department typically require an expensive replacement. In other words; no vacuum means no ignition, which may be why you are experiencing cold air when you're expecting hot. Next, use fine-grit sandpaper to remove any oxidation from the tip of the pilot, and reattach the pilot tube to the furnace. Let’s look at some of the solutions to this common furnace problem. This is a likely cause if your furnace blows hot air, then cold. Furnace Blowing Cold Air? 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. The electronic trouble code is 8, which means the gas pressure is low I have changed the gas valve and the flame sensor … read more Your thermostat has an ON and AUTO switch that runs your blower. Check for an air duct leak, particularly, leaks from cold areas such as an un-heated crawl space or basement into the return air duct system. Cold air trapped inside will need to be expelled before the hot air can take its place! If gas or oil you can certainly verify whether or not the burner is shutting down when you'd expect it to keep running. It is important to note that constant overheating can damage your heat exchanger. While the system is in cooling mode, the frost that had built up on your outdoor coil then turns to water, runs … If you own a gas furnace, there are several potential things that can cause cold air to blow when you're expecting hot. As a pilotless burner owner, you'll want to keep your fingers crossed that your issue isn't related to your burner's circuitry. 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. When the fan is on, the furnace will continue to blow, regardless of whether or not the air is being heated. In fact, the problem may be as simple as changing your filter! If you've recently had an electric power surge or any other power issue, the fix could be as simple as replacing a fuse or flipping the circuit breaker. Use care not to touch an HSI when troubleshooting or installing a new one. Possible Conclusion 1: It’s Not Blowing Cold Air. Unfortunately, it isn't uncommon for an HSI to malfunction. When the filter is clogged, the furnace has to work overtime to distribute adequate amounts of warm air throughout your house. There are many reasons your car's heater isn't working. Or the gas line isn’t supplying enough gas to your furnace. Your thermostat has a switch for your fan that can either be set to “on” or “auto.” If this switch is set to “on,” then … Then, use a pipe cleaner or other small brush to remove any clogs within the supply tube. If your furnace ran out of fuel, or was simply low on fuel, this could be your problem. When the furnace is … And if it's the dead of Winter, this can be a serious problem that needs immediate attention. The motor can be faulty or seizing up causing it to not spin fast enough to move enough air through the furnace. Excessive heat or exposure to water can damage the circuit board, which can cause your furnace to lose some or all of its functionality. Once it hits the set temperature I'm guessing the gas will cut off and the fan will continue blowing. I have an electric furnace that blow cold air sometimes. One safety bypass he made was found during the repair and corrected. Upon dissection of draft motor is was covered with white crusty minerals probably from the water from the humidifier mounted on the nearby cold air return. The fan setting on your thermostat has two options, “on” and “auto”.

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