Why Is My Furnace Blowing Cold Air?

February 5, 2021
Family Furnace

During the cold winter months, your air conditioner is essential in maintaining comfortable indoor air quality. Everyone enjoys curling up in a cozy house when it’s cold, and the last thing you would ever wish to experience is a faulty furnace that blows in cold air. Even if you’ve got a relatively new unit, a lot can go wrong, causing this unpleasant experience.

However frustrating a faulty furnace can be, fixing it is the only way to solve the issue. Some cases require professional attention. However, you can quickly resolve some minor issues so your family won’t have to stay too long in the cold. Here are the most common reasons why your furnace might blow cold air into your living space.

1. It’s at the Beginning of Its Heating Cycle

If you notice cold air a few minutes after turning on your furnace, there’s nothing to worry about. It could be that your furnace hasn’t warmed up yet, and you need to give it a few more minutes. It’s normal for the unit to blow in cold air first before the warm air comes in. If your home’s furnace only blows in cold air for a short period and then it gets warm, that is completely normal. However, if warm air doesn’t follow after a few minutes, consider other causes discussed below.

2. Wrong Thermostat Settings

If the air coming out of the vents seems rather cold and your house isn’t receiving the required heat, check your thermostat’s settings. Generally, a furnace has “on” and “auto” options. When it’s in the “on” position, your fan will keep running, but the unit will not heat the air. The fans will only blow out room-temperature air. If that’s the case, turn the switch into the “auto” setting. The thermostat will detect that the house temperature differs from the set conditions and immediately kickstart the furnace to heat up and circulate warmer air.

3. Faulty Thermostat

It’s worth noting that the thermostat communicates your house’s heating needs to the furnace. Hence, if it doesn’t work, then the furnace may blow in cold air. If your thermostat isn’t communicating with the furnace correctly, this could result in your furnace blowing cold air.

Also, if you have recently gotten a new thermostat and have installed it on your own without consulting a professional, you might have picked a thermostat that’s incompatible with your home’s heating system. As a result, it can communicate the wrong instructions to your furnace. To stop the cold air issue, have an expert inspect your thermostat. You can even upgrade to a programmable one for better efficiency.

4. Clogged Filters

Gradually, dirt, dust particles and other debris can build up on the filters of your furnace or in your HVAC system, limiting airflow. As a result, the temperature may rise in the furnace, and when it gets really hot, the limit switch automatically shuts down the heating cycle. At this point, the fan continues to run to cool the furnace and protect it from damage, which results in cold air circulation.

If you can, look for the filter compartment on your furnace and take out the access door. Pull out the filters and replace them. Ensure that you follow all the manufacturer’s instructions on proper positioning. Remember to put back the access door and check whether the heater blows in warm air. If you have a problem replacing the filters, seek professional assistance.

5. Inadequate Gas Supply

If your gas supply shuts off and there’s no fuel in the furnace, there will be no heat production. In such a case, your furnace may lock down for safety purposes if it fails to get the required amount of gas to produce warm air. First, check whether the gas valve is on. If you turn it on and still get cold air, there could be a problem with your gas supply line. You will need to let a professional handle this issue.

6. Dirty Flame Sensors

A pilotless ignition furnace uses a flame sensor to keep burning. If your unit begins to cycle on and off, you probably have a dirty flame sensor that prevents your furnace from staying lit. In case the sensor notices that your burners aren’t working, it can shut them off for safety reasons.

When dirt clogs the flame sensor, it causes it to turn the burners off prematurely so that your furnace won’t have a heating source. As a result, cold air will blow out of your unit. It would be best to have experienced technicians clean the flame sensor.

7. The Pilot Light Could Be Out

In an older furnace, when the pilot light goes off, its thermocouple automatically shuts off the burners, so your furnace can’t heat the air. To relight it, turn off the furnace’s power, look for the pilot light assembly and turn the switch off. Give it some time, around 15 minutes, to let the escaped gas clear off. Next, reset the switch to “pilot” and light the outgoing gas using a match. Once lit, turn the switch back to “on.” If you don’t feel comfortable doing this, it would be best to reach out to a professional.

8. You Have an Overheated Furnace

The furnace works by heating a group of metal coils, and heat exchangers transfer the produced heat from one point to another. When the air blows over these coils, it picks up the heat. At times, your furnace can get extremely hot, especially when there is limited airflow, which causes the unit to shut down. The fans remain in operation, and they thus recirculate cold air.

It’s worth noting that repeated overheating can ultimately damage your unit, resulting in expensive repairs. Once you notice such signs, replace the air filters immediately. If the overheating persists, call in a professional to look at your unit and determine any other possible issues.

9. You Have Leaking Ducts

Your unit can sometimes blow in cold air when hot air escapes through leaks in the ductwork. By the time the air reaches your house, it no longer feels warm. Have an expert check and repair the duct to prevent cold air from seeping into your home.

10. Clogged Condensate Drain

Highly efficient furnace models contain a condensate drain that helps remove water generated during the heating process. If the drain line blocks, the overflow kill switch turns off the burner to prevent water damage.

To resolve this, turn off the power, look for the condensate pan, remove the water and dry it. You can also attach a vacuum at the opening of the drain line to suck out clogs. Restore the power unit to see if the furnace works.

Quality Furnace Care

When a furnace blows in cold air, it could be because of one of the above issues. You can prevent most furnace problems by scheduling regular maintenance. If your furnace still blows in cold air after trying out the above suggestions, seek professional help from C & C Heating & Air Conditioning. We provide cooling and heating services in the greater Metro Detroit area and the surrounding regions. Our company is made of a team of skilled and certified technicians, and we guarantee high-quality services.

You can reach out to us for air conditioning, duct cleaning, indoor air quality tests, mini-split units and emergency repair services. We also deal with AC and furnaces installations, repair and maintenance jobs. Connect with us today to schedule an appointment and enjoy our top-notch services.

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