Why is My AC Not Blowing Cold Air?

Is your central AC not blowing cold air?

During the sweltering heat of the summer months, a malfunctioning air conditioner can be both uncomfortable and hazardous for your health.

That’s why you need to identify the potential cause of the problem as soon as possible to get your air conditioner running again. The more information you have, the better you’ll be able to address the issue and return to living comfortably.

What causes it

Whether you have a dirty air filter, a refrigerant leak, a frozen evaporator coil, or otherwise, you need to know the warning signs. Today, let’s take a look at the most common issues with home air conditioners and help you get your cold air blowing again.

  Honeywell Home thermostat in heat mode.

Your Thermostat Settings are Incorrect

If your home is hotter than it should be with your air conditioner blowing, your first trip should be to the thermostat. Sometimes, thermostats that run on batteries may lose power suddenly. Once you’re sure it’s in working order, make sure you have it set to blow cold air. Some thermostats have settings for cool, warm, and fan. Double-check that nobody in your home has accidentally changed it from its usual thermostat settings.

Once your AC unit kicks on again, set it to a lower than usual temperature setting and give it a few minutes. Then, place your hand over your nearest air vent and check to see if it’s blowing cold air. If it works, you’re in luck – you don’t have to read any further! Otherwise, you’ll need to continue reading for more troubleshooting tips for your air conditioning system.

Replacing your thermostat

Many homeowners are comfortable changing their thermostats. A common mistake is not buying a thermostat that matches the capability of the system. This could limit the capacity of your system or prevent it from properly cooling. Straight cool air conditioners and furnaces will have a different thermostat than a heat pump system.

Very often homeowners prefer simple easy-to-use thermostats. Most of the higher-efficiency heating and cooling systems are multi-staged. A simplified thermostat may not be compatible with these AC units.

Use caution

If you choose to replace your thermostat, be sure to closely follow the manufacturer's instructions. Many homeowners experience system shutdown after replacing their thermostats. Crossed wires can blow fuses, burn up transformers, and even damage control boards. This leads to much more costly repairs.

dirty air filter sitting in place

You Have a Dirty Air Filter

Your central air conditioning system relies on easy access to circulated indoor air to return cooled air to your home. The system's indoor air return system has an air filter in it designed to remove airborne particles and prevent dust and debris from returning to your home through your air ducts. But if you haven’t replaced your air filter recently, your fan coil blower motor could shut down after overheating when failing to suck in enough air.

It’s critical to check your system's air filter as often as you can. If you can’t see through to the other side of the air filter or if it’s turned a gray or brown color from collecting too much debris, you may need a brand new one. Some clogged filter brands, though, are washable – this means you can scrub it clean and put it back into the air conditioner unit to try again.

Not just a cleanliness issue

Dirty air filters may also cause your evaporator coil to freeze up. If you found that you had dirty air filters, you may have to wait for the evaporator coil to thaw before you'll begin to feel cool air blowing again.

A quick way to check if this is the case is to go to your indoor air handler unit and listen to hear if the blower fan is running. If it is running and not blowing air out of your vents, your evaporator coil may be frozen solid. You will want to contact an HVAC professional if this is the case.

A dirty filter equals a dirty coil

Failing to regularly change the filters in your AC system could also result in a dirty indoor air coil. Household dust and other airborne particles adhere themselves to the wet surface of your evaporator. This sets up conditions for biological growth and odors. Most importantly, it inhibits the cooling process. This stops your AC unit from removing the heat energy and prevents your system from cooling properly. This will result in higher energy costs.

Yellow Jacket refrigerant leak detector finding R410 leak on evaporator coil.

You Have a Refrigerant Leak

Most people know the chemical coolant, also known as the refrigerant, that helps to create cold air: Freon. Freon flows through your AC’s indoor and outdoor coil, drawing heat energy and humidity from the air and releasing it outside. While you should only have to add Freon to your central air conditioner once, a refrigerant leak reduces the system’s ability to cool the air. If you discover a refrigerant leak in your central air conditioner, it has to be fixed ASAP. Otherwise, the problem will only get worse.

You need a license

However, since Freon is a chemical regulated strictly by the EPA, only people with professional licenses are allowed to handle it. You’ll need to reach out to your local HVAC maintenance company to help you repair the leak and refill the coolant in your air conditioner to get it up and running again.

Do the maintenance

The refrigerant levels in air conditioners should be checked annually. A heat pump should be checked twice per year. Refrigerant leaks typically occur in the evaporator or condenser coils. Refrigerant leakage from these components or anywhere in the condenser unit is easy to find with a freon detector. This is also the best way to identify a faulty compressor.

The hard-to-find leak

Leaks in the refrigerant lines (or line-set) can be difficult to identify, locate, and repair. The line-set is copper refrigerant tubing that connects the outdoor condenser unit to the indoor portion of your HVAC system.

These lines are almost always routed through walls, crawlspaces, and attics. This may sometimes lead to additional costs to find the leak. Your HVAC technician may need to pump down all of your refrigerant and pressurize your system with nitrogen to find it.

Fieldpiece leak detector finding freon leak in evaporator coil

Your Air Conditioner’s Condenser Coil May Be Dirty

During the coldest months of the year, professional HVAC technicians recommend protecting outdoor systems from snowfall and other debris that may go unnoticed for months. If your air conditioner is not blowing cold air, you should check your condenser unit to ensure it’s not covered in dirt, leaves, or other debris.

Keep the area clear

Another big cause of an air conditioner, not cooling is vegetation or structures built too close to the outdoor unit. If you have vines growing around or inside of your AC unit, remove them quickly so they don’t grow and constrict the unit any further. Proper operation of the system relies on the unit's ability to transfer heat to the outdoor air. Also, maintain constant vigilance to prevent toys, towels, tools, and other objects from ending up on top of your air conditioner. Otherwise, it may not be able to operate at optimal capacity and could have worse problems down the road.

Problems a clogged condenser coil will cause

Every outdoor central air conditioning unit is comprised of two main parts: the condensing coil and the compressor. A clogged condenser coil will cause several issues including the following:

  • Compressor malfunctions

  • The air conditioner not cooling properly

  • Overheating and damage to the condenser fan

  • System shutdown

  • Damaged contactor

Clogged air conditioner condenser coil

vegetation growing too close to heat pump condenser

Your Evaporator Coil is Frozen

Inside your central AC unit, you’ll find something called an evaporator coil. Evaporator coils are typically found within the fan coil cabinet – especially if your device is part of a heat pump system. As warm air flows into the evaporator coil, thermal energy and humidity are removed. Then, the conditioned air is pumped back inside of your home through the air ducts, making it cooler and less humid.

How to tell

There are a few ways to notice if you have a frozen evaporator coil:

  • Poor ventilation throughout your home combined with warm indoor air

  • Frost building on the copper tubing leading into the coil cabinet

  • Higher energy bills each month

  • Runoff condensate near your device in larger amounts than usual

  • Formation of frost on the external refrigerant tubing or outdoor unit

Another issue related to a frozen evaporator coil is the condenser. If your home air conditioner system is no longer blowing cold air and no other explanation is found, you should have this checked as well.

If any of these signs are present in your air conditioner, you may need to call in an expert. Replacing your air conditioning unit’s evaporator coil is something only trained HVAC professionals should handle on their own.

Frozen evaporator coil on Amana package unit

You Need to Call in an Air Conditioner Professional

Once the hot weather hits, you know you’ll need a powerful air conditioner in your home. If you experience your AC not blowing cold air, you may find yourself and your family in a miserable condition within a few hours.

As you can see from the list above, there are quite a few potential reasons why your home air conditioner isn’t working properly. And sometimes, it may take the eyes of a licensed HVAC technician to get your system back to tip-top shape. If you’d like to enlist a professional Knoxville, TN area AC repair company to take a look at your system, contact the team at Blue Water Climate Control today.

Written by Jeremy James

Jeremy James is a veteran of the U.S. Navy who has grown his family's HVAC business into one of the most successful home service businesses in Knoxville, TN. More than 20 years of experience in the HVAC and Engineering industries and passion for what we do has translated into our customer service, professionalism, and quality. LinkedIn

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