Why Isn't My AC Blowing Cold Air?

Ben Giesbrecht

When your ac conditioner decides it's time to take a break, it's usually in the dead of summer when an ac system is needed the most. This can be very frustrating and sometimes scary to us as homeowners. Sometimes we have company coming over or even worse, an elderly person can't be left in a blistering climate.

The first thought that comes to mind is, "it's going to cost so much to get fixed". Hold that thought for a second because a lot of times an ac not blowing cold air can be fixed without calling an expert out.

Let's run through some common problems that might be the reason your air conditioning system isn't blowing cold air.

The Temperature Setting is Set Wrong

This may seem extremely obvious but let's start at square one. The thermostat is what controls your central air conditioner. If the thermostat settings are incorrect, it will be the first thing to correct.

Your air conditioner will only turn on when the temperature is set cooler than the room temperature. Make sure the thermostat is set to a cooler temperature than the room.

Another thing to check is the heat and cool setting. If your air conditioning system is set to "heat" instead of "cool" it's probably what made your ac stop blowing cold air.

Once you have switched the settings to "cool" make sure you complete the first step of ensuring the temperature is set right.

If the problem doesn't go away after adjusting to correct settings, the thermostat itself could be the problem. If it uses batteries, check them and, where necessary, replace them. If the problem is still there after this, move on to the next step.

You Have a Dirty Air Filter

A dirty or clogged air filter will restrict airflow and has to be taken care of. When the air conditioner is on, the air filter works overtime trapping dust, pollen, lint, hair, and other airborne particles in order to keep the rest of the ac system in working order. If the air filter becomes clogged, the ac is under stress and might cause the air conditioner to stop blowing cold air.

When the system's air filter is plugged like this, there is restricted airflow into your home, leading to your ac not blowing cold air. Without enough air supply, it may cause a system shutdown.

If you fail to maintain your air filter, it is a sure way to shorten the life of an ac system. In worst cases, it may even damage the condenser unit and evaporator coil.

Make sure to clean your filters regularly and replace them at least once every three months.

Clogged Drain

Air conditioners remove moisture from the air, with the water typically draining out a hose or drain pipe which can become clogged with algae.  This prevents water from backing up into your home or the unit and causing damage. The piping sometimes needs to be replaced, but can usually be cleaned with a mild bleach solution.

Faulty Evaporator and Condenser Coils

While the air filter will do its best to keep the evaporator and condenser coils clean and efficient, the coils will still wear out over time. If exposed to moisture, your indoor evaporator coil can start growing mold and mildew over time.

Another thing that can make an ac stop blowing cold is a clogged condenser coil. Over time, the condenser unit collects dirt, grass, leaves, and other particles of outdoor air. Cleaning the condenser coils in the outdoor unit every year is something most people don't get done.

When air conditioning systems start blowing warm air, a good check of these coils is crucial to make sure they are properly maintained.

If you are a DIY person, you will be able to figure out how to clean these coils with minimal research.  If not, your local HVAC company will be happy to perform maintenance.

Frozen Evaporator Coil

An evaporator coil is part of the indoor portion of the central air conditioning system. If your indoor appliance is a refrigerator, the evaporator coil is located outside the furnace in its own drawer. 

The evaporator coil is located within the fan coil cabinet if the indoor device is a fan coil (typically as part of a heat pump system). Warm indoor air flows into the evaporator coil, which removes thermal energy and humidity. 

The air is then pumped back into your house, making it cooler and more relaxed. Below are some symptoms of a frozen evaporator coil:

  • Frost is building on the copper refrigerant tubing that leads to the coil cabinet.
  • Insufficient ventilation.
  • Increased energy costs.
  • Condensate runoff near your indoor device is excessive.
  • Frost formation on external refrigerant tubing or the outdoor unit in serious situations.

The causes of a frozen evaporator coil are usually traced back to a lack of proper maintenance.

Restricted Duct Work

A central air conditioner system is fed by a maze of passageways called ducts that lead to registers and vents. Registers and vents work by channeling air into the AC unit as well as blowing conditioned air indoors.

Both the supply vent and return air register play a crucial role in supplying consistent airflow into your home. Always keep your supply vents open to ensure uniform cooling throughout your space.

Properly cooling your home can be affected greatly if ductwork that is connected to the vents and registers is blocked or leaking. Leaks in the ductwork reduce your home's cooling by letting cold air escape to the attic or through the walls.

Cold air blowing through a blocked duct also affects the ability of your ac unit to cool efficiently. Air conditioners rely on efficient duct systems. If some ducts have too sharp of a bend or are totally pinched off indoor air quality is sacrificed.

An HVAC system also needs good airflow. If the airflow is blocked somewhere it can affect the life of your air conditioner system by adding extra strain on it.

If you are suspicious of leaky or restricted ducts, an HVAC professional from our team will be happy to check the ductwork out and get your air conditioner cooling properly again.

Refrigerant leak

Your AC's refrigerant plays a crucial role in the cooling process of your air conditioner. As it cycles between the indoor and outdoor systems through a sequence of compression and evaporation, it absorbs all the hot air in your living space.

If the copper tubing refrigerant lines start to leak, the refrigerant reduces and will not absorb as much heat and humidity as before. The outcome is a hotter and more humid living space.

If you think you have a leak somewhere in the system's indoor or outdoor components it needs to be addressed as soon as possible. Refrigerant is pricy and the sooner the leak in your air conditioner is fixed, the better it will be.

Keep Your AC Efficient With an Expert

The lifespan of a central air conditioning unit greatly depends on how it has been maintained over the years. An ac not blowing cold air usually starts from improper maintenance.

This means making sure all filters are cleaned and changed regularly. Components from the outdoor condenser unit such as the condenser coil and condenser fan need to be serviced at least once a year.

Involving an HVAC expert in your routine maintenance is a great way to stay on top of potential problems in your air conditioner system. Our heating and air experts will perform thorough regular maintenance. If there is a problem, we can correct it before it causes a larger problem down the road.

Summarizing Why Your AC Won't Blow Cold Air

After reading this post you have probably figured out there are a lot of things that can cause an air conditioner not to blow cold air.

As stated many times, a lack of maintenance is usually the start of the problem. The performance of air conditioners is taken for granted a lot and we forget the many moving parts that need some love every once in a while.

Why Should You Choose Us When Your AC Isn't Blowing Cold Air?

Our goal is to provide our customers with the best service possible. We strive every day to leave customers satisfied and bring them into a long-term relationship with us. Our team is committed to changing the traditional "Chuck and a truck" methods of service, and providing you a heating and air service you will never forget. If you have an ac not blowing cold air, we will be here to resolve it efficiently, and cost-effectively.