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Seven Common HVAC Airflow Problems And How To Solve Them

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A functioning HVAC system should be an aspect of your comfortable living that largely goes unnoticed.

Keeping your home cool and humidity at bay should be something you enjoy yet largely do not pay attention to.

Until it goes wrong and then you simply cannot escape it. 


In this guide, we will look at some common HVAC system problems and detail the solutions to fix them.

Of course, if you are in any doubt as to what the problem may be or how to solve it then contact a qualified air conditioning specialist to take a look.

The Common HVAC Problems And Their Solutions

Whatever the problem is with your HVAC system, in most cases hoping that it will solve itself will result in rising energy costs and suffering from fluctuations in temperature and airflow.

Several issues could result in the air not getting from the furnace or air conditioner into the relevant parts of your home. 

The problems could include air filters that need to be replaced or clogging with your air vents and condensate line.

If something is wrong with your furnace or coils then you will need to get that rectified promptly while a leaking refrigerant simply cannot be ignored as it will prove dangerous. 

The Incorrectly Sized Air Conditioning Unit

Size does matter and buying an air conditioning unit that is too big does not mean higher efficiency.

An oversized air conditioning unit can mean short cycles that are too large and too long so the system frequently turns itself on and off. 

With more likelihood of wear and tear, over time your unit cannot provide the airflow you desire and fails to remove excess moisture as it is not on for long enough. 

If the air conditioning unit is not big enough then it is forced to work harder to effectively cool your home.

This increased dependency can overheat many of the components and especially the capacitor. 

Perhaps you were wrongly advised when the HVAC system was installed yet an air conditioning specialist should be able to assess your living space and recommend the right size of the unit.

Dirt Covered Air Filters

To do their job properly, air filters will trap pollutants and tiny particles. However, over time you may notice that the air quality drops, especially if anyone in your home smokes.

There is a really easy solution to this problem and you should aim to replace your air filter every two months to keep the air fresh. 


It can be highly distressing when you have set the air conditioning unit to its lowest setting yet the room remains unbearably hot.

That weak airflow and poor circulation may mean you have to put your hand on the vents simply to check whether any air is coming out at all.

This kind of airflow problem can be easily attributed to a blocked air vent or clogging somewhere in the HVAC system. 

Air Ducts

Should it feel like there simply is not enough airflow in your home then there could be a clog somewhere in the system.

This could be your air ducts which can be blocked with dust or even be obstructed by foreign objects. 

You can solve this yourself by removing every single register in your home and checking to see if you can spot any potential buildup of dust or an object close to the opening.

If not, you could ask an air conditioning specialist to carefully inspect the ductwork.

Condensate Line

Another clogging problem could be attributed to the condensate line.

This is a vital component in your air conditioning unit as it removes the water that drips from the coils.

As a relatively small and enclosed space that will contain moisture, mold can quickly grow and build up to clog the line.

Part of your regular maintenance for the HVAC system (see also ‘What Is HVAC System And How Does It Work?‘) should be cleaning the condensate line every month.

You will need some typical household items and this should not take very long at all.

Begin by turning off the power for your air conditioning system at both the breaker panel and thermostat. 

The drain line should be outside and will be a PVC pipe located by the condenser unit though if you live in an apartment building it should be in the same closet as your water heater.

Carefully remove the cap then gradually pour a single cup of either peroxide, bleach, or distilled white vinegar into the line and let it sit there for half an hour to clear up any blockage.

Outside Air Conditioning Unit

Outside Air Conditioning Unit

The outside air conditioning unit can also experience clogging, especially when it faces extreme weather conditions.

While it may be able to stand up to the wind and rain, pesky leaves can get into the inner workings of the unit. 

You may want your plants to hide the eyesore from the rest of your garden yet those leaves and typical garden debris can make it difficult for the unit to disperse any heat and determine the airflow.

Keep checking the outside unit whenever you pass it and clear any visible debris to stop this problem from occurring. 

Hot And Cold Spots In A Single Room

If there is an uneven airflow in your home which results in hot and cold spots in certain rooms then you will want to balance that out.

This can both improve air circulation and go some way to improving the air quality.

You may even see a reduction in your energy bills due to hot and cold spots causing unnecessary stress on your air conditioning unit.

There are some simple steps you can take to solve this problem and one is to prevent drafts by keeping your doors and windows sealed.

Keep the air vents clear and make sure they are visible as obstructions such as furniture can disrupt an optimal airflow. 

Even something as straightforward as keeping electronic equipment away from the thermostat as any heat that is generated can force the thermostat to believe that that room is warmer than it is. 

Furnace That Fails To Pump

The furnace in your HVAC system should be a pretty trustworthy piece of equipment yet if it comes on but fails to pump the hot air through your vents then there could be several problems that can be responsible. 

Typically, this is down to a malfunctioning furnace fan which seems fairly obvious.

To try and troubleshoot the problem, turn the furnace off then switch to the ‘fan only’ setting on your thermostat, and keep your ear out for the fan turning itself on.

Hopefully, that solves the problem and it should be a noticeable sound. 

If you still cannot hear any action after a few minutes check the circuit breaker to ensure that the specific switch for your furnace is activated.

You should check with an air conditioning specialist to see if there is a problem with the wiring of your fan.

Should the switch not be off then it may be that the furnace fan (see also ‘ How To Wire 3 Speed Fan Switch’ ) or even the thermostat could be due to a change.

Another switch to check is the limit control switch which tells your fan if it should turn itself on or off.

This is another problem that is best looked at by an air conditioning specialist as it could be an overriding factor over the poor wiring or circuit breaker.



A leak can be the most traumatic of HVAC airflow problems and if you discover one you should quickly get in touch with an air conditioning specialist.

A leak can be caused by expanding joints in your ducts which result in gaps allowing the air to escape before it hits the prescribed destination.

In the meantime, you can use some duct tape to seal the leakage.

If the leak is refrigerant then this is particularly dangerous as breathing it in can be poisonous.

The warning signs include an HVAC system that fails to actively cool your home, frost on the condenser unit, and even a hissing sound that can indicate that the refrigerant is leaking. 

You may even feel the symptoms of this leaking refrigerant yourself when you begin to suffer from a scratchy throat, headaches, dizziness, general nausea, and irritation in your eyes. 

There is no time to waste and you should contact an air conditioning specialist promptly.

Malfunctioning Coils

The coils are a vital component of your HVAC system as the air passes over them and cools down to effectively cool down your living space.

They can malfunction due to various issues including if they are covered in dirt which interferes with the airflow and how they deal with heat. 

This problem can eventually lead to compressor failure and your home feeling warm.

Cleaning them can be straightforward and involves shutting off the power to the air conditioning system and spraying some compressed air all over the coils to remove the dirt. 

The coils can also be frozen which can occur when you fail to change your air filters as moisture from the coils drips into the drip pan.

This moisture can eventually freeze resulting in a large piece of ice that blocks the airflow and results in higher energy costs and an inefficient air conditioning system. 

Looking after the coils should be another regular job that is involved in air conditioning maintenance so you could perform this yourself or hire specialists to do it.  

Final Thoughts

Several problems can result in poor airflow from your HVAC system.

Some can be very simple to diagnose and solve while others will require an air conditioning specialist to take a look. 

Regular maintenance should go some way to ensuring that you can avoid certain problems such as dirty air filters or a clogged air conditioning unit.

However, an issue such as a refrigerant leak needs to be resolved as soon as possible.

Frequently Asked Questions

Before you leave us, check out our FAQ section to get your last-minute questions answered! 

How Do I Troubleshoot Airflow Issues?

Start with the thermostat and check that it looks to be functioning properly.

Then there are the air filters to check and replace if they are clogged and dirty.

The air ducts could also be blocked so check that they are free from any obstructions.

Finally, check the outside air conditioning unit to make sure that it is free of any garden debris. 

How Can I Increase The Airflow In The Ducts?

This can be relatively straightforward and includes cleaning the ductwork and air filters as a buildup of dirt can restrict the airflow.

You could also add some inline duct boosters as well as air dampers to ramp up the airflow in certain weak areas.

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