Each winter, some homeowners in Northern Kentucky and the Cincinnati area come home after a long day only to be greeted by a furnace that’s blowing cold air. When temperatures dip near or below freezing, this is an issue you need to resolve quickly to restore comfort to your home.
In our most recent blog, the technicians at Rusk Heating and Cooling discuss common reasons why your furnace might be blowing cold air and how to fix it. We also explain when it’s time to call in the pros, so read on below!
Incorrect Thermostat Settings
Sometimes, the reason behind a furnace that’s blowing cold air is as simple as a thermostat that has been set incorrectly. Make the thermostat your first stop for troubleshooting this issue.
- If the thermostat is set to COOL instead of HEAT, your furnace won’t run at all. Make sure HEAT mode is selected on your thermostat.
- Your furnace may also be blowing cold air because the fan is running continuously. When the fan ON setting is selected, the furnace blower fan runs at all times – when AUTO is selected, it only runs during a heating cycle. If the fan runs continuously, it will push cold air through the vents between heating cycles, which can make it seem as if the furnace is blowing cold air.
Dirty Furnace Filter
If your furnace’s filter is clogged with too much dirt and debris, it can restrict airflow through the system. The temperature inside the furnace will increase, eventually tripping the high limit switch, which will shut off the burners and allow the furnace time to cool down. The blower fan may still continue to run, pushing cold air out the vents.
- Check the furnace filter. If you hold it up to a light and no light passes through, it’s definitely time for a new filter.
- Be sure to replace the filter with a new one. Replace the filter according to the airflow indicator arrows printed along its frame.
Pilot Light is Out
If you have an older furnace with a pilot light ignition, your furnace may be blowing cold air because the pilot light has gone out.
- Turn off the furnace.
- Open the access panel to see if the pilot light is out.
- Find the pilot light reset switch, and turn it to the OFF position.
- Wait about five minutes to allow gas in the area to dissipate.
- Next, turn the switch to the PILOT position and depress the switch.
- Hold a flame to the pilot to relight it, then turn the switch to the ON position.
- Watch the pilot light to make sure it does not go out again. If it does, fix any drafts in the area, which may be responsible.
- Replace the access panel, and turn the furnace back on.
If the pilot light continues to extinguish, call your technician for repairs as there may be a malfunctioning thermocouple or other issue with the assembly system.
Condensate Line Clog
Newer high-efficiency furnaces produce condensation as combustion byproducts convert from gas to liquid. If the condensate drain line that allows moisture to flow out of the furnace becomes clogged, the system’s overflow kill switch stops the furnace operation to prevent water damage. This is a common answer to why your furnace is blowing cold air in homes with this type of heating system.
- Clean out the drain line by attaching a wet/dry vacuum to the exterior exit point of the line and allowing the vacuum to run.
- If you suspect ice is forming and causing the clog, install heat tape or pipe insulation around the drain line to prevent reoccurrence.
Furnace Repairs in Northern Kentucky and Cincinnati
If your furnace is blowing cold air, we recommend trying the troubleshooting steps above first. If these steps don’t restore heating in your home, call us to request service for furnace repairs. Rusk Heating and Cooling performs fast and reliable furnace repairs to keep your family comfortable all winter long.