furnace blowing cold air

A Troubleshooting Checklist for a Furnace Blowing Cold Air

If your furnace is blowing cold air, and you’ve already done some troubleshooting but still can’t figure out why, then your furnace needs to be thoroughly checked. A complete troubleshooting guide should help you solve the cold air troubles within a short time.

We’ll share a complete checklist of things to look for when having a problem with your furnace

Why Is My Furnace Blowing Cold Air?

First, it’s crucial to find out why your furnace is blowing cold air to choose a befitting solution. Some of the common causes of this cold air problem include:

  • The thermostat setting is incorrect
  • Furnace filter is blocked with dust or debris
  • The furnace blower is not working
  • Airflow is obstructed in furnace ducts, furnace intake, or furnace outlets

One or all of these malfunctions could be the reason your furnace is blowing cold air. You should check and rectify every looming problem to ensure that your furnace can produce warm air again.

Here’s a complete troubleshooting checklist for your furnace.

Check the Furnace Power

The first thing to check is furnace power. Make sure it’s turned on and working correctly. If your furnace is electric, check the circuit breaker box in the house for a tripped breaker switch that may have caused an outage of electricity supply to the furnace unit. Check furnace switches and furnace wall plugs for power.

If the furnace is gas-powered, ensure there is sufficient airflow by checking furnace intakes or furnace outlets. If these aren’t present, call a repair company immediately because this could be indicative of a more severe malfunction, such as carbon monoxide infiltration within your house or leaking fuel gas.

Again for gas-powered furnaces, turn the furnace off and relight it with a match or lighter to ensure there are no leaks in your fuel line. If you smell gas when turning on the furnace, do not attempt to light the stove yourself because this could result in an explosion.

Check the Thermostat Settings

Turn up your thermostat’s temperature to see if it is set too low for the furnace to kick in properly. If you have an older model, this may be why your furnace won’t turn on. Some old models only have settings that indicate either “off” or “on,” whereas newer furnace models may have settings for low, medium, and high.

Your thermostat could be on low settings, hence the furnace blowing cold air.

If you have a furnace used for both heat and air conditioning, check the thermostat settings to see whether there’s an option for fan-only mode. If your furnace still blows cold air after turning up your thermostat’s temperature settings and checking that it isn’t set on low, then check your furnace settings and furnace wiring. Some furnace models have this setting, so it could be the reason why your furnace isn’t blowing hot air.

If it’s set to fan-only, change the furnace settings to allow the furnace to blow warm or hot air and see if this remedies the problem.

Check the Furnace’s Circuit Breaker

Head to your furnace’s circuit breaker panel (or where you switch power off) and check whether it has tripped. If this is the case, then resetting the furnace will cause it to start working again. 

Check the Furnace Filter

Another reason why the furnace is blowing cold air could be a dirty furnace filter. If you have not cleaned the furnace filter for quite some time, it might be clogged with debris and need to get replaced right away. Check whether this remedy has helped by switching on your furnace’s fan and furnace blower. 

Check the Furnace’s Inlet Ducts

If your furnace still blows cold air, you might need to check whether there is a blockage in the furnace’s intake ducts. Blocked furnace intake ducts could be preventing adequate airflow. You can disconnect each of these ducts and clean them with a vacuum cleaner. 

Check Fuel Level

If your gas furnace is blowing cold air and won’t shut off, check the furnace’s fuel level in its tank. The furnace may blow cold air due to a low gas furnace supply if it is running out of fuel. If your electric furnace is blowing cold air, ensure there are no tripped circuit breakers or blown fuses. These might be preventing adequate power supply from getting into your furnace unit, thus causing the furnace to blow cold air. 

Rectify Overheating Issues

Ensure that the furnace’s heat exchanger is not overheating. If it does, your furnace may be blowing cold air due to an overheated furnace heat exchanger. A faulty gas furnace pressure switch might also overheat and cause the furnace unit to blow cold air. Ensure that this part is clean and free from debris build-up as well. 

Check the Furnace’s Gas Pressure 

Your furnace might be blowing cold air due to a high furnace gas pressure or nitrogen oxide concentration in the furnace chamber or too low an amount. Check with your furnace manufacturer for more information on setting up gas pressures correctly. 

Ensure there are no Obstructions Present in Furnace Vents 

If you have central air conditioning in your home, the furnace may be blowing cold air because of an issue with this system instead. It is also possible that there are obstructions present in furnace vents. Ensure that all furnace vents are clean and free from debris build-up before calling a professional for help if the furnace itself is blowing cold air.

Call a Furnace Repair Company for Help

If you’ve tried everything above, but the furnace is still blowing cold air, it may be time to call a furnace repair company for help. There could be further issues present that require professional attention. 

However, if your furnace has been working fine despite these factors for years without issue, it may be time to consider replacing your furnace with a more energy-efficient model. Ensure your furnace is always under maintenance and constant inspection to minimize surprise breakdowns and cold air problems.

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