Why Is My Furnace Blowing Cold Air?

Why Is My Furnace Blowing Cold Air?

If your home furnace is blowing cold air throughout the property when you want it to provide warm air, it can cause severe disruption to your quality of life. Moreover, it indicates that the gas furnace is not performing as it should.

A furnace repair or replacement will be the only way to restore the gas furnace’s function, safety, and efficiency. The first step, however, is to find the answer to ‘why is my furnace blowing cold air?’ as an accurate diagnosis will enable you to implement the right ideas to bring your HVAC system back to its best.

Why is my furnace blowing cold air throughout the home?

Why Is My Furnace Blowing Cold Air?

A heater blowing cold air can fill you with fear, especially if you’re not an expert in HVAC system repairs. In most cases, it doesn’t mean the entire unit is broken. In most cases, it indicates a problem with an individual component used during the heating process.

The good news is that a professional HVAC technician can usually repair the damage straightforwardly and affordably. Here are some of the heating cycle components that may have become faulty, thus causing the unit to start blowing cold air.

The thermostat has been wrongly programmed

Even when the gas furnace performs at full efficiency, it will only blow out air as instructed by the thermostat. So, if your heating system blows cold air, it is important to check the settings first.

You probably won’t want hot air during the summer, so this issue will only be noticed once the colder weather arrives. If you have forgotten to switch the thermostat setting to Heat, the furnace will keep blowing cold. 

Meanwhile, it will continuously blow air if you’ve left it set to On. So, if the heater isn’t needed at a specific moment, you will be left with cold air. Programming the thermostat to Auto could solve your issues.

The pilot light is damaged

The pilot light ignites the furnace burners and subsequently plays a vital role in ensuring that Heat is achieved. While a furnace should last up to 20 years, a faulty pilot light could occur sooner.

You can often relight the pilot light yourself using a standard lighter. You will know that the simple furnace repair has worked because the pilot light will turn blue, and the furnace will begin to blow hot air rather than cold air once more.

Many newer gas furnaces do not feature a pilot light. So, if you experience this issue, it may still be worth calling a professional, as other faults and damages could impact older furnaces.

Your gas supply is too low

When a furnace burner fails to deliver hot air, it may also be due to poor gas supply to the home. Your furnace has a safety feature designed to switch off if it does not receive the amount of gas needed to perform, which can cause it to blow cold air even if it is in good health. 

It can be a serious issue that has no easy fix—as such, calling a reliable HVAC technician is pivotal. 

The duct sealing is broken

Why Is My Furnace Blowing Cold Air?

Hot air has to travel a long distance from the furnace to the air vents. Unfortunately, if your air duct sealing has holes in it, the warm air will be allowed to escape. As such, it will seem like the furnace is blowing cold air when it is just escaping through the cracks.

Worse still, when this is the source of your problems, your energy bills remain just as high because it is technically blowing hot air. The most effective way to overcome this issue is to either fix or replace the duct sealing.


The air filter is dirty

Blowing cold air is one of the most common symptoms. When the airflow is restricted by dust, debris, and foreign materials, it can impact the furnace in many ways. As well as preventing your home from reaching the desired temperature, those particles can cause your family health issues. 

A long heating cycle may also indicate that a dirty air filter needs to be replaced. It is a quick, easy, and affordable job that will improve the home’s air quality as well as the efficiency of the furnace.

If your furnace doesn’t have a pilot light, it will feature a flame detector. Allowing dirt and dust to cover this component will cause significant heat loss. Once cleaned, it should start blowing hot air once more.

The furnace has overheated

Finally, if the furnace is blowing cold air, it could be that the unit has overheated. The team needs a chance to cool down before it can blow hot air again. When this happens, a safety feature shuts down the system to prevent the threat of fires or explosions.

Depending on the model, you may need to flick a switch. Crucially, though, you must also investigate the reason why the furnace overheated. It could be age, dirt blockages, or mechanical failure. A precise diagnosis will influence your next steps.

How to fix a heater blowing cold air

Why Is My Furnace Blowing Cold Air?

As the above shows, a furnace blowing cold air is often attributed to basic faults requiring equally simple treatments. However, you cannot stop it from blowing cold air if you do not know the root cause of your problems. 

In most cases, it means repairing the faulty component so that hot air can return. However, an older furnace may require a replacement. Here at Air Ace Heating & Cooling, our friendly experts can provide a complete diagnostics service, followed by impartial and honest advice on what steps should be taken next.

Either way, a qualified HVAC professional is the best person to repair the furnace and restore your peace of mind. Get in touch with our friendly team to fix your gas supply and make cold air problems a thing of the past.


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