The Furnace Is Blowing Cold Air: A Troubleshooting Guide
The middle of a harsh Ohio winter is no time to be confronted with a furnace blowing cold air. You want to curl up in a cozy house after you deal with harsh weather conditions, so it’s time to take a look at the reasons the furnace may be blowing cold. Some issues with the heat are easy to fix, but others require a qualified professional to get you away from the space heater and back to a house that’s warm all over.
Check the Thermostat Fan SettingIf your furnace’s blower fan is set to run continuously, it runs even when the system is not working to produce heat. Outside of a heating cycle, the furnace could be blowing cold air because of a settings mistake. Go to your thermostat and take a look at the fan setting. Make sure the switch is set to AUTO, not ON. With the AUTO setting chosen, your furnace should only run the fan during a heating cycle and not push cold air through your vents in between.
Thermostat Not WorkingSince your thermostat communicates your home’s temperature needs to the furnace, if it isn’t working correctly, your furnace could blow cold air because it isn’t receiving the right instructions from your thermostat. Replacing your thermostat ensures accurate communication with your furnace to stop cold air issues. Have your thermostat replaced by your HVAC technician, and consider upgrading to a programmable or smart thermostat for better control over indoor comfort and energy consumption.
Check Furnace Air FilterA dirty air filter hinder air movement through the furnace. This raises temperatures inside the furnace, and the limit switch shuts heating cycles down if the unit becomes too hot. If you have a dirty filter, replacing the filter typically stops cold air from blowing.
- Find the filter compartment on your furnace, remove its access door if applicable.
- Slide out the old filter and dispose.
- Insert a new one of the same dimensions into the filter compartment. Make sure you follow the directional markings noted on the filter frame for proper positioning.
- Replace access door to the compartment, if applicable.
Broken Furnace Control PanelWhen a furnace blows cold air, there may be an issue with the unit’s electronic control panel. This is sometimes easily solved by resetting the system.
- Turn off power to the furnace at its ON/OFF switch.
- Wait a few minutes, then flip the switch to ON.
Pilot Light Is OutIf your furnace’s pilot light goes out, the furnace will blow cold air because combustion of fuel is not taking place. The pilot light needs to be relit to burn fuel and heat your home.
- Turn off power to the furnace.
- Locate the pilot light assembly and turn the reset switch to OFF.
- Wait 10-15 minutes to allow any escaped gas to clear the area.
- Turn the reset switch to PILOT. While doing so, use a lighter or match at the pilot end to light outgoing gas.
- Once the pilot is lit, turn the switch to ON.
- Restore power to the furnace.
Standing Water Around UnitHigh-efficiency furnaces produce condensation, which normally exits the system through the condensate drain line. If there is a blockage in the line, the system’s overflow kill switch turns off the unit to prevent water damage. Standing water around the furnace is a sign of a condensate line blockage. Clear condensate drain clogs with these steps:
- Turn off power to the unit at the breaker.
- Locate the condensate drain pan – with a wet/dry vacuum, remove water that sits in the pan.
- Remove and clean the pan with mild dish soap and water, then replace.
- Follow the condensate drainpipe that extends from below the pan to its exit outside your home. Attach your wet/dry vacuum to the opening to suck out clogs.
- Restore power to the unit.