If your furnace is blowing cold air, it can make your home, and your family, uncomfortable! There are a few reasons why your furnace might be letting in the cold during the winter. Some of them are simple fixes that you can take care of yourself. For others, you may need to call a PRO. Let’s look at why you might have cold air blowing from your vents.
The Fan is Running
If your fan is running when your furnace is not heating the air, it is just circulating room temperature air. The air feels cooler as the temperature in your home gradually drops. The good news is, this is an easy problem to correct! Check your thermostat’s fan setting. If the fan setting is “On” then your fan will be on all the time. Set your fan to “Auto,” so the blower only comes on when the furnace is heating the air.
You Have a Dirty Filter
Dirty or clogged air filters are another problem that can cause your furnace to blow cold air. A dirty filter can reduce the airflow to the heat exchanger and can cause it to overheat. When it overheats, your furnace may trip the high limit switch, causing the burners to shut off to prevent damage. Turn your furnace off at the thermostat and change out your filter, then turn it back on.
A quick note on air filters: We’ve found that if you use a HEPA filter in your furnace you are likely to experience the same issue. Due to their dense nature, HEPA filters restrict airflow in the same way that a dirty filter can.
The Pilot Light is Out
If you have an older furnace with a pilot light, it might not be lit. When your pilot light isn’t lit, then the burners won’t light, and your heater won’t heat. If you are confident in relighting the pilot yourself, then follow these steps.
- Turn off your furnace on your thermostat.
- Remove the cover on your furnace and find the pilot light assembly and reset switch. They should be near the bottom of your furnace.
- Turn the knob to “Off” and wait 5 minutes to shut down the gas to the unit.
- Turn the knob to “Pilot” and push in to restart the gas flow. As you press the knob, hold a lighter or match to the pilot opening until the flame lights.
- Turn the knob to “On.” Your furnace should ignite. You can then turn the furnace back on at the thermostat.
If you aren’t sure how to do this, or if the pilot won’t light or stay lit, it’s a good idea to call a PRO.
You Have Dirty Flame Sensor
If you have a newer furnace, you probably have a flame sensor rather than a pilot light. A flame sensor keeps the furnace burning once it starts. However, if it is dirty, your unit may begin to heat and quickly turn back off. We suggest cleaning the flame sensor if you are familiar with it, or give the PROs a call for a furnace inspection and cleaning.
The Condensate Line is Clogged
High-efficiency furnaces have a condensate line that runs from the unit to a floor drain. The condensate line removes water during the heating process. However, if that line gets plugged with dust, dirt, or mold, or if the condensate pump fails, it can cause the water to back-up into the furnace. A back-up will cause trip an overflow kill switch that shuts down the unit to prevent water damage. If you notice water pooling around the base of your furnace, this is most likely the problem, and we recommend calling a professional to assess any damage to the unit and remove the clog.
Give It a Little Time
Sometimes, it can take a little bit for the air blowing through the vents to feel warm. Wait several minutes to see if the air heats up. Your furnace might need a little time to get going. If it never gets warm, and you’ve gone through the list of possible causes, it’s probably time to call in an HVAC technician to diagnose any issues your furnace has. As always, if you have any questions or concerns, don’t hesitate to call the PROs at 303-660-9831!