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My AC Is Blowing Warm Air: What Is Going On?

AC blowing warm air into a white kitchen

There’s nothing quite like the cool relief our air conditioners bring us on hot summer days. After running errands, playing with the kids outside or taking the dog for a walk, we expect to open the door and enter a nice, cool atmosphere. This is why it can come as quite a shock when you step through your door only to find that your house is warm. After some investigating, you may realize that warm air, and not a cool blast, is blowing out of the vents throughout your home.

Unfortunately, there is no easy answer as to why your unit might start blowing warm air. While some of these issues warrant professional help, there are certain steps some homeowners may feel comfortable doing on their own, especially those who are familiar with how HVAC systems work. Before we dive into the more serious issues, let’s touch on those smaller problems first.

Thermostat Setting Is Wrong

The first thing you should do if you feel hot air coming from your vents is to check your thermostat to see if your thermostat is set to “heat” instead of “cool”. While this may seem silly, you would be surprised how often this is the culprit! This can easily happen on accident when cleaning or when kids are playing nearby. If it is set to “heat,” flip the switch to “cool” and your system should start blowing cool air.

Return Vents Blocked

Return vents are where your home’s system pulls in air. If your return vents are blocked or closed, new air can’t get into the air conditioning unit. That means that the only air that can blow over the evaporator coils is the air inside the unit itself. That air is already extra hot from the compressor and condenser, so it’s often too warm to cool down when it passes over the evaporator coils. As a result, you’ll feel warm air coming from the vents. Fixing this problem may be as easy as opening or unblocking the return vent.

Air Filter Is Dirty

Dirty air filters cause warm air just like blocked air returns do. Fresh air can’t make it inside the unit and it starts to struggle. Check your air filter regularly to make sure there’s no dirt and debris buildup on it. If it’s clogged, it will do more harm than good. While there are many different factors that go into how often you should change your filter, you should typically change your air filters every three months. If you own pets or use your air conditioner more frequently, you’ll likely want to replace your air filter are on a more regular basis.

Dirty Condenser Coils

Over time, condenser coils get dusty and dirty, due to rain, wind and other conditions. This buildup of dust, leaves, dirt and vegetation can make it difficult for your condenser coils to push air outside. This can lead to the same problem as a clogged filter or a blocked return vent, which can also drive a large spike in energy consumption. While cleaning your condenser coils is a relatively easy task, most homeowners don’t have the tools to properly clean these specialized parts, so many homeowners leave this job to the pros.

That takes care of the “easier” issues that might be causing your problem. If you’ve ruled these possible causes out, troubleshooting gets a bit tougher and more complex. Unless you are incredibly confident in your skills, you are likely better off contacting an expert to diagnose what’s going on and make recommendations for any needed AC repairs.

Outdoor Unit Is Off

A home’s outdoor unit runs on a separate electrical supply than the fans inside the house. If the outdoor unit loses electricity for some reason, or if your outside AC unit is not running but your inside unit is, your home’s fans will just blow air through an inert machine. When this happens, you’ll feel nothing but warm air.

A compressor that shuts off unexpectedly is usually the result of a tripped breaker or a blown fuse. While this may seem like a simple fix (after all, you can flip a breaker, right?), both of these problems usually mean that something electrical is wrong with your outdoor unit. In this case, the easiest option is to reach out to a professional. Electrical problems are rarely a good fit for a DIY solution, especially with a power draw as high as an air conditioning unit.

That being said, there’s no harm in double-checking to see if the breaker has been turned off. If too many appliances running at once caused the breaker to trip, you can try flipping it back on to see if that works.

Low Refrigerant Levels

Finally, on rare occasions, there may be a pinhole leak somewhere in your system that allows refrigerant to escape. Without enough refrigerant in your system, the evaporator coils can’t absorb heat. The consequence is that your air conditioner turns into a fancy fan for room temperature air. Again, not something you want to try to deal with on your own, as refrigerant can be dangerous if inhaled.

Although it’s almost always in your best interest to contact a professional when in need of air conditioner repair, there are some is some maintenance you can try while you wait for your professional to arrive. If you have the right tools and consider yourself to be a pretty handy person, you can begin with cleaning your condenser coils.

dirty condenser coils

How to Clean Condenser Coils

Over time, dirt, pollen, leaves, rain and other debris can make your condenser coils dirty, making it difficult for them to work properly. This buildup acts as insulation, which leads to condenser coils that never lose heat, refrigerant that never returns to a liquid state and an air conditioning unit that doesn’t actually cool your home.

A dirty condenser coil can cause other problems, too. If you notice your energy bill skyrocketing or your unit running on high all the time, you could have dirty condenser coils. Fortunately, if you have all the right tools, cleaning your condenser coils isn’t too difficult of a task. Here are the steps involved:

  • Turn off the power to your unit.
  • Inspect the outside of your unit for any debris that has collected on the coil guard. This wire mesh helps prevent the coils from getting damaged and is typically the first place where debris collects.
  • Brush off the outside with a coil brush or an old hairbrush. Your goal is to remove debris like tall grass, leaves or dirt that’s caught in the guard.
  • Check your coils to ensure that none of them are damaged. If some of your coils have small bends, you can straighten these yourself with a fin comb. However, if you notice significant damage to your coils, you’ll need to have a specialist advise you on the best next steps.
  • Gently wet the coils through the coil guard using your hose on a gentle spray.
  • Apply a generous amount of coil cleaner to your coils. This kind of cleaner can be purchased at your local hardware store.
  • After about ten minutes, or based on the product instructions, rinse off the coil cleaner. This should cut through run of the mill dirt and grime and get your system back in working order.

Most of the problems we’ve discussed thus far don’t have much of an impact on you and your family, aside from the fact that you may be uncomfortable in your home and have abnormally high energy bills. However, if you’re dealing with a refrigerant leak, there could be more serious consequences. This means it’s important to be able to recognize the signs of low refrigerant.

A white and gray living room

Low Refrigerant Symptoms

The final issue that can cause warm air to come out of your air conditioner is low refrigerant. In a properly-maintained system, the refrigerant level should never change. The refrigerant lives in a closed system and the amount is supposed to remain constant.

That said, there can be problems associated with your refrigerant level. Gaskets can fail, pipes can crack and refrigerant can escape out of your air conditioner and evaporate away. A low refrigerant level will cause many problems, and being able to identify the signs of low refrigerant can help you catch needed repairs before the situation becomes a much bigger problem.

Lower refrigerant levels in your unit will first lead to the air conditioner being less efficient. You’ll notice that it takes longer for the house to cool down, and your system will be running more often. A low refrigerant level means the unit has less capacity to cool, so your energy bills will be higher than normal and your home will not be a comfortable temperature.

Another symptom of low refrigerant is frozen evaporator coils. Refrigerant relies on pressure to shift between liquid and gas forms. Lower pressure in the refrigerant system changes the temperature generated when the refrigerant evaporates in the evaporator coil. The low-pressure refrigerant absorbs so much heat at the coils that water vapor freezes to them. Frozen evaporator coils can then cause your air conditioner to freeze up, which leads to even more problems with your system and its parts.

If you get close enough to the leak, you might be able to hear a hissing or bubbling, depending on the location. If you detect either of these noises coming from your air conditioning unit, you’ll want to call a licensed professional to come take a look.

Finally, and most importantly, it’s important to catch refrigerant leaks early because of the impact inhaling refrigerant can have on your health. In gaseous form, refrigerant has no smell or color which can make it difficult to detect. However, if you have been exposed to refrigerant, you may begin to experience signs of refrigerant poisoning, which include headaches, dizziness, nausea and, in severe cases, breathing difficulties and loss of consciousness.

A refrigerant leak should always be fixed by a licensed technician. Refrigerant is never supposed to “run low.” A leak means that more refrigerant needs to be added and AC repairs need to be made. Heating and cooling technicians understand how to recharge refrigerant and how to seal gaps without risking the rest of your unit.

ABC Can Quickly Diagnose and Repair Any AC Problem 

Air conditioning units are complex and a seemingly small problem can quickly turn into a large, costly headache. No matter what is the cause of your malfunctioning unit, you can rely on ABC Home & Commercial Services to get your system up and running again. Our licensed specialists can help with any heating and cooling service you may need, whether you want advice on how to change your filters, if you’re dealing with a refrigerant leak or if you have another problem entirely. With ABC’s help, you won’t have to wait for long until your home is cool and comfortable again.

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