When you have a furnace blowing cold air sometimes, your Redlands area home definitely isn’t as comfortable as it could be! Allowing this issue to continue could cause great energy waste and the longer you ignore it, the more damage your heating system could incur. Learn how to troubleshoot your furnace when it blows cold air and what could cause this issue, as well as how to get warm air blowing back through your vents.

Furnace Blowing Cold Air Sometimes – What to Do

Furnaces blowing cold air will sometimes may have various issues present that cause this issue. Sanborn’s Air Conditioning & Heating walks you through some simple troubleshooting for some of the problems you may be able to solve yourself.

Dirty Furnace Filter

A dirty air filter is a common culprit of furnaces blowing cold air. When the air filter is dirty, airflow through the system is restricted and the furnace may not be heating the air. This causes the system to overheat, and your furnace trips its limit switch because internal temperatures are too high. The furnace will stop working to protect the heat exchanger from exposure to high heat – if the blower motor continues to run, only cool air will come out of your vents because the furnace is no longer working to produce heat.

  • Turn off your furnace.
  • Remove the air filter from the filter compartment and inspect it.
  • If the filter’s surface is caked with contaminants, it’s time to replace it.
  • If the furnace does not start back up after it has cooled and the air filter has been replaced, you may need to call a technician to reset the limit switch.

Fan Settings

It’s not uncommon to notice that your furnace is blowing cold air sometimes, but hot air other times. Often, this issue is caused by the fan settings of the thermostat. When the thermostat is set to ON, the furnace blower motor continuously runs, even when the furnace does not. When the furnace is off and no heat is produced, cold air will be blowing from the vents. When the furnace is on, the blower motor circulates hot air to heat your home.

  • Check the thermostat and the thermostat fan setting.
  • After you check your thermostat, make sure it is set to AUTO – this allows the blower to run only while the furnace does. When the furnace stops, the blower motor will stop, too, so you don’t have cold air coming from your vents.

Water Around Furnace

If you have a high efficiency furnace, it produces condensation. Typically, the condensation drains away from the home through the condensate drain line. However, if a blockage is present, condensation will back up and trigger the overflow kill switch which shuts down the furnace to prevent damage. Water on the floor around your furnace is a clear sign of this issue. To clear condensate line clogs, do the following:

  • Turn off power to the furnace at your home’s electrical panel.
  • Find the condensate drain pan.
  • Using a wet/dry vacuum, pull out all water that has gathered in the pan.
  • Detach the pan and clean it with dish soap and warm water. Rinse, dry, and replace.
  • Find the exit point of the condensate line by following the tube to the outside of your home.
  • Attach the wet/dry vacuum to this opening and turn it on to pull out any clog material.
  • Once finished, turn power back on to the system.

Get Fast Furnace Help Now

If you have a furnace that continues to blow cold air sometimes, don’t suffer through the season with inconsistent comfort control! Call Sanborn’s Air Conditioning & Heating to repair your furnace fast! Our technicians take over when troubleshooting isn’t enough, performing reliable repairs to help your furnace run flawlessly throughout the winter season. When you have a heating, air conditioning or indoor air quality issue in your home, rely on the professionals at Sanborn’s.