furnace blows hot air then cold
It has always done this. Ductwork is often installed in areas such as attics, garages or crawl spaces where there isn't temperature control. Let’s look at some of the solutions to this common furnace problem. If this doesn't resolve your cold air problem it could be the themostat itself, but before calling a professional, we recommend trying the other troubleshooting suggestions first. When I turn the furnace off and then back on again from the thermostat it then blows warm air again. Apologies for the delay. Unfortunately, it isn't uncommon for an HSI to malfunction. Thermostat: A Furnace Blowing Cold Air Could be Due to Your Thermostat. But if it doesn't light, or it won't stay lit, you'll want to check that gas is flowing to the pilot. Unfortunately, more complex issues in this department typically require an expensive replacement. It has a clean air filter in it also. 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. When the furnace resumes heating, I see the normal flashes of 20 green followed by one red. 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. 3) Pilot light is out If your gas furnace is only blowing cold air, then the pilot light may be out. If the gas is on, but the pilot won't light or stay lit, the pilot tube or orifice may be dirty. 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. 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. As soon as the furnace cycles back on the air will warm up again. 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. FURNACE BLOWS COLD AIR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. Continue reading at FAN LIMIT SWITCH TROUBLESHOOTING or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX. 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 … This issue is often caused by the thermostat receiving false readings. I swear you will soon find an answer to your problem with your heat pump 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. Your thermostat has an ON and AUTO switch that runs your blower. If your furnace is blowing cold air, or is not operating at all, a component called the fan limit switch may have malfunctioned. You’ve got three basic options. 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. You may also see an error message on your thermostat, or a blinking LED light on the furnace control board. The lukewarm air coming out of your furnace can also be the result of leaky air ducts. In other words; no vacuum means no ignition, which may be why you are experiencing cold air when you're expecting hot. If we close them the heat will stay on longer and it will get too hot. If the flame stays on, great! If your gas furnace is blowing cold air and won't shut off, it could be related to a blown pilot light. If you own an electric furnace and it's blowing cold air there's a few things that could be causing the problem. Again using Occam’s Razor, we can assume that the next likely culprit for your heater blowing cold air is your thermostat. By switching the thermostat to “auto,” the fan will only blow when the furnace is heating the air. Weâve replaced the flame sensor, the filter is clean. (No not recently.). Pilotless furnaces have been an energy-saving breakthrough for the home and commercial heating industries. When heat called for and fan comes on it blows cold air, then heat, then cold, then off. This is a likely cause if your furnace blows hot air, then cold. Since the draft motor was noisy we replaced that as well. Recent information. Furnace operating problem. Not sure if I can do a quick fix somehow? Next, use fine-grit sandpaper to remove any oxidation from the tip of the pilot, and reattach the pilot tube to the furnace. The flame sensor itself is relatively easy to clean, but many homeowners are uncomforable working on their furnaces. Oddly he does not complain during the really cold weather. If you choose to call a professional to do the job for you, this would be a good time to have your system inspected. A dirty air filter blocks airflow over the furnace’s heat exchanger, causing it to overheat. According to the book the 2 red flashes means "Retries or recycles exceeded". Excessive heat or exposure to water can damage the circuit board, which can cause your furnace to lose some or all of its functionality. 2. Gas furnaces produce air that is 130-140°F range. Another telltale sign is if your utility bills are higher than they should be based on use. This “hot then cold air” sequence happens over and over and your home isn’t warming up. At the time the furnace is blowing cold air, I see two slow green flashes followed by 2 quick red ones. Once every few days, the furnace will kick on as normal, send out heat, but after a few minutes weâll notice that itâs blowing cool air. Your body temperature is around 98.6°F (everyone’s body temperature is slightly different, but that’s the average). Since then the downstairs apartment gets cold (like 62-64) with the thermostat set to 68. To mitigate carbon monoxide and puff backs, an internal motor kicks on and creates a vacuum just before the burner engages. 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. If I shut if off for a few minutes and then try again, about half the time it will blow hot air. Is your furnace not blowing hot air? If the vacuum does not occur, the furnace will not ignite. Would it matter if the return/supply "loop" for each apt were separate somehow? Your furnace may be blowing cold air because the filter is too dirty. The thermocouple is a sensor that regulates ignition, and if it requires adjustment or replacement your furnace will blow cold air. I would start by looking at the furnace itself: is this an electric, gas or oil unit? 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. This will eliminate the risk of freezing. If gas or oil you can certainly verify whether or not the burner is shutting down when you'd expect it to keep running. Check that the air filter is clean and that the ductwork is not obstructed. The major issue that can cause this problem is a heat exchanger issue. 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. It is important to note that constant overheating can damage your heat exchanger. Furnace overheating can be the cause of your cold air dilemma. When the condensate drain freezes, it causes condensation to drip back into your system and trigger a shutdown. Compromised flame sensor. When we first owned this house we have removed the humidifier (and installed a whole house water filter). The motor can be faulty or seizing up causing it to not spin fast enough to move enough air through the furnace. What Can I Do If My Heater Is Blowing Cold Air? (This is just on general principle). There's a lot of issues that can cause your ducts to leak. If your fan is set to "on," your furnace will continue to blow cold air until the drain thaws. Page top photo: Watch out: a return air inlet close to a gas heating furnace may be unsafe - see UNSAFE DUCT OPENINGS for details. This can … An HSI or Hot Surface Ignitor is the most popular way to ignite a pilotless furnace. More diagnostic details are at FURNACE FAN CYCLES DURING HEAT, Our 22 year old furnace just started having intermittent problems. Your thermostat’s fan setting. I do not dare force it. This can be a little bit confusing, so let’s clarify it carefully. When the furnace is … 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. If left, it will just keep blowing cool air. But still the same issue. While the system is in cooling mode, the frost that had built up on your outdoor coil then turns to water, runs … Furnace Blowing Cold Air? We have owned home 12 years. When your furnace is blowing cold air your warm and inviting home can turn into an icebox in a matter of hours! Use care not to touch an HSI when troubleshooting or installing a new one. 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. Your furnace blows hot air but that air quickly turns cold then the furnace shuts off altogether. 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. Or maybe the air starts off hot, then turns cool before the furnace shuts down. 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. 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. Depending on the type of burner you have, it isn't uncommon to experience any of the issues listed above. 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. Leaky ductwork can cause serious issues for your heating system. 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