During the cold weather, the last thing you will ever want to experience is a furnace that blows in cold air. Even if your furnace is relatively new, some situations can lead to malfunctioning. While some issues require an expert approach, you can quickly troubleshoot and fix others. Read on to understand various reasons why you’re getting a blast of chilly air from your furnace.

1. The Filter Is Too Dirty

Dirt clogs the filter, restricting airflow over the furnace heat exchanger. As a result, the temperature rises in the furnace, and the safety control shuts off the burners. It ends up blowing in cold air.

The solution is to find the filter compartment in the furnace, slide it out, and replace it with a new one. After changing, your furnace should begin blowing in warm air.

2. Incorrect Thermostat Setting

If your house doesn’t feel as warm as it should, the heater may not be blowing in warm air. Therefore, the currents flowing through your vent will feel cold. Chances are someone got hot and turned the thermostat fan setting to “ON.” Simply flip the switch back to “AUTO.”

3. The Pilot Light Is Out

When the pilot light goes off, the heater doesn’t light the fuel to heat the house, so the furnace blows cold air. This mostly happens when there’s an interruption in the gas supply that prevents fuel combustion from taking place. In this case, check your manufacturer’s instructions to determine how to ignite the pilot light. The process of igniting the pilot light may differ across brands.

If you feel comfortable doing it, turn off the furnace’s power, find the pilot light assembly, turn off the valve, and let the gas purge out for about 10 to 15 minutes. Next, set the switch to “PILOT,” light the outgoing gas using a match, turn on the button, and restore power at the furnace.

If the light fails to remain lit for a more extended period, it might be due to a clogged opening. Switch off the gas valve and clean the space. If it still doesn’t work after several attempts, there could be a thermocouple problem. This will require professional assistance.

4. Leaking Duct

If your duct contains some large holes, the heated air may escape, which will make it so the air doesn’t feel warm once it reaches your room. Besides that, cold air will get into the duct and blows into your home. When you start experiencing cold chills, you may want to check the ductwork. Most of the time, you’ll be able to check ductwork via the basement or attic. Examine all exposed areas for leaks.

If you spot some openings, seal them using professional-grade duct tape or aerosol duct sealing. You may also want to have your ductwork inspected, insulated, and sealed by an expert to minimize heat loss.

5. Dirty Flame Sensor

If your unit blows in warm air, then quickly turns relatively cold, the problem could be the flame sensor. When the flame sensor is worn out or clogged, your furnace will begin heating for a moment and then quickly turn cold. The dirt causes the burner to keep shutting off, pushing cold air through the system. If you’re well familiar with the furnace components, you can clean the flame sensor to restore the heating function. Otherwise, leave this to a professional.

6. Overheated Furnace

When your furnace gusts warm air, then cold, and stops blowing anything after some time, chances are it’s overheated. It occurs when you don’t change the filters often enough, resulting in compromised airflow. When this happens, the safety functionality shuts down the burner, and you’ll begin to feel cold air coming out of your vent.

When you notice this, it would be wise to change or clean the filters immediately. Constant overheating may affect the heat exchanger, leading to expensive repairs.

7. Clogged Condensate Drains

Highly efficient furnace models contain drain lines that remove the excess water generated during the heating process. They have a sensor that prevents the burners from lighting when the lines get blocked. The sensor turns off the unit to prevent water damage. As a result, you’ll experience some cold air blowing from it.

You can easily detect this issue by checking around the furnace. If you notice standing water, then you have a clogged condensate drain. To fix this, turn off the power, look for the condensate drain pan, and remove any water from the pan.

Follow the condensate drainpipes that extend to the outside section of the house. Using a dry or wet vacuum, suck out any blockage. Restore the power, and the sensors will automatically detect that you’ve removed the clogs and allow the furnace to work again.

8. Inadequate Gas/Oil Supply

If your gas line fails to provide enough fuel to warm up the air, the furnace locks down for safety purposes. Therefore, it’ll keep circulating cold air. This regularly happens when you try to turn the unit on after having it shut off for the summer. You might also turn off the valve in the process if it lies perpendicular to the line. The solution to this issue is turning the valve to the open position.

Another reason is that you might have run out of gas. It’s worth noting that you can either connect your gas furnace to your city’s natural gas line or to a personal propane tank. If you use your own personal fuel tank, it will be best to check it often to ensure it doesn’t run out. Look at the pressure gauge frequently, and when it gets below 15%, ask your suppliers to fill it up.

If you get your fuel from an underground line supply, call your provider to confirm they haven’t shut you off. If the gas source isn’t the problem, you’ll need to have a professional check to see if you have a broken line.

9. The Thermostat Isn’t Working

Remember that the thermostat communicates your house’s temperature requirements to the furnace. If it’s inefficient, it might signal the wrong instructions, which could explain the furnace blowing cold air. Change the batteries if you’ve used the thermostat for a while without doing so.

You could also be using a thermostat that’s incompatible with your system, or it might be installed incorrectly. You may also have a defective thermostat.

If you turn the heat on and the air doesn’t get warmer after a few minutes, turn the thermostat up and stand near the furnace. You should hear some clicking sounds that indicate the heater’s producing heat. Nonetheless, if there’s total silence, chances are you have a bad thermostat that needs replacement.

Seek Professional Help

You can easily prevent most furnace-related problems through regular maintenance. If you’ve tried all the above steps and your furnace keeps blowing cold air, you need professional assistance.

Reach out to All Hours Plumbing and Drain for both residential and commercial services. We’re a highly experienced plumbing and HVAC company that offers services in Utah, Davis County, Salt Lake, and Park City. Our services include heating installation, repair, and maintenance. We also handle drain cleaning, emergency plumbing repair, and air conditioner maintenance.