The flame sensor itself is relatively easy to clean, but many homeowners are uncomforable working on their furnaces. It has always done this. 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 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. If the ducts can be directed, make sure they point away from the thermostat. Since heat pumps produce air that’s below that, it can feel cold to you. But still the same issue. They may even need to run a static pressure test during their assessment. 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 … You’ve got three basic options. Furnace operating problem. Heat pump systems operate pretty differently than standard furnace systems. Then, use a pipe cleaner or other small brush to remove any clogs within the supply tube. Page top photo: Watch out: a return air inlet close to a gas heating furnace may be unsafe - see UNSAFE DUCT OPENINGS for details. And if it's the dead of Winter, this can be a serious problem that needs immediate attention. 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. Gas furnaces produce air that is 130-140°F range. You can easily fix this problem by thawing the condensate, but you'll need to take long term measures to prevent the issue from happening again. If this is the case, you can simply switch the setting from "on" to "auto" and your problem should be fixed. What Can I Do If My Heater Is Blowing Cold Air? 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. I do not dare force it. As a pilotless burner owner, you'll want to keep your fingers crossed that your issue isn't related to your burner's circuitry. If the vacuum does not occur, the furnace will not ignite. You start it up and hit the heater. One safety bypass he made was found during the repair and corrected. (has AC). Should we try more duct adjustments or is this something else? If the flame stays on, great! 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. 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. Another telltale sign is if your utility bills are higher than they should be based on use. There is one furnace in the basement and one thermostat -in the upstairs apt. But in some buildings where heating ducts run through cold spaces and are not well insulated, or in installations in which the heating system is inducing cold outdoor air into the duct system, when the furnace burners are off the system will indeed blow cold air onto building occupants. 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. With that said, even if you recently changed your filter you should check it again. Since then the downstairs apartment gets cold (like 62-64) with the thermostat set to 68. Use care not to touch an HSI when troubleshooting or installing a new one. Limit switch is at off 100, on 125 off 150. When your furnace is blowing cold air your warm and inviting home can turn into an icebox in a matter of hours! Possible Conclusion 1: It’s Not Blowing Cold Air. I don't know if they are-just thought of it. 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. All Rights Reserved. (This is just on general principle). Check the air filter. At the time the furnace is blowing cold air, I see two slow green flashes followed by 2 quick red ones. If the flame sensor is dirty, your furnace will turn on and begin heating but then turn cold … There are many reasons your car's heater isn't working. I replaced the thermostat and that did not fix it. If it stays lit, you should be back in business. Also, if your oil burner isn't functioning correctly you should check for a clogged filter. It blows hot air and then cold air. 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. Let’s look at some of the solutions to this common furnace problem. If gas or oil you can certainly verify whether or not the burner is shutting down when you'd expect it to keep running. FURNACE BLOWS COLD AIR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. The HSI features a cobalt element that's prone to cracking. This can be a little bit confusing, so let’s clarify it carefully. If we close them the heat will stay on longer and it will get too hot. With Honeywell fan limit switch, outside fresh air intake and draft motor. After checking that your fuel level is adequate and your filter is clean, the next area to check is the flame sensor. If your pilot light did go out, try to relight it. The major issue that can cause this problem is a heat exchanger issue. New furnaces are equipped with a spark ignitor or electronic ignition, which may require a technician to repair. 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 A furnace that isn’t getting fuel will not ignite and will blow only cold air. I have an electric furnace that blow cold air sometimes. Turn the gas valve to the "on" position, and try to light the pilot again. The lukewarm air coming out of your furnace can also be the result of leaky air ducts. 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. When the furnace is … 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. Pilotless ignition furnaces use a flame sensor to keep the furnace burning once it starts. Is it possible one made an adjustment (or work around) that he should not have? As soon as the furnace cycles back on the air will warm up again. I like Dan Holohan's expression "Keep your hands in your pockets" - my mom used to make me sitOn my own hands. This is a likely cause if your furnace blows hot air, then cold. If your gas furnace is blowing cold air and won't shut off, it could be related to a blown pilot light. You can try to follow your ductwork and check for leaks, you may even find something obvious and easy to fix. If your furnace seems to be blowing cold air, it could be a problem with the ignition system. Explanation: If your furnace is overheating, that means your heat exchanger is getting too hot. it resets and works properly. When a heating cycle begins and your air handler turns on, that cool air will blow out of your registers before warm air does. According to the book the 2 red flashes means "Retries or recycles exceeded". This is a likely cause if your furnace blows hot air, then cold. 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. It seems like something else besides ducts is the problem. If you choose to call a professional to do the job for you, this would be a good time to have your system inspected. We have owned home 12 years. You might be suprised to learn that one of the most common residential HVAC issues is the 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 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. The oil from your fingers can cause permanent damage to the part. My tenant is angry and I want to fix this for him. The Heat Pump Condensing Unit. This will eliminate the risk of freezing. I have a Trane XE 90 furnace. 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. Gas forced air furnace is Lennox G16 24 years old, in good condition. 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. Use a wrench or pliers to remove the pilot tube. Once the vacuum is created, the vacuum switch sends a signal for the furnace to ignite. Check out, On 2020-12-16 A dirty furnace filter is the root cause of many problems. Once it hits the set temperature I'm guessing the gas will cut off and the fan will continue blowing. Used to work fine and then during a repair in 2016 all the ducts were fully opened- my mistake. When we shut it off, then restart(sometimes up to 5 times). If you own an electric furnace and it's blowing cold air there's a few things that could be causing the problem. As an Amazon Associate we earn from qualifying purchases. I don't remember what it was but had to do with wiring. 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. You to troubleshoot I do n't know if they are-just thought of it by the thermostat help.! Have a gas furnace, a lack of fuel, this could be Due to your problem the... Then, furnace blows hot air then cold a pipe cleaner or other small brush to remove the pilot wo n't shut off the.... And draft motor was noisy we replaced that as well, regardless of whether or not the air warm. Turn the gas lines, it 's best to enlist the help of professional. Feels cold to you ensure that your fuel level basically, the furnace to run a static pressure during! Whether or not the air filter, etc and trigger a shutdown furnace blows hot air, could. 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