Air conditioners are workhorses that do more than make life easier in the summer. They reduce humidity and keep your family healthy by fighting allergens and promoting comfortable, restorative sleep. When the A/C malfunctions, it ruins more than your day. 

Understanding Common A/C Problems

Five Air conditioners for Understanding Common AC Problems

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Air conditioning units are not a luxury, but a necessity. A reliable A/C not only cools everyone off while indoors, but it also regulates humidity in your home. Controlling the temperature in your home is better for pets, elderly, children, and individuals with allergies.

Ever notice it seems like you’re A/C unit usually malfunctions on the weekends or holidays – and always outside of normal business hours? The problems may be simpler to fix than you think, and many of those are avoidable with regular in-home, inexpensive, care and maintenance.

A good A/C unit should last a minimum of ten years, and larger units can last up to twenty, but not without at least an occasional checkup. We have put together a list of tips and tricks to tackle the most common A/C problems out there.

How an Air Conditioning Unit Works

How an Air Conditioning Unit Works

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A/C units have been around since 1902 and while the capacity, efficiency, and cost changed immensely over the years, the basic premise on how an air conditioner works is standard. It is all about heat transfer. A/C units move the heat built up in your house to the outside environment.

Before you can start basic troubleshooting for A/C problems, one must first understand how the unit works and some of the terms a technician might reference.

  1. Evaporators are cooling cools that remove both heat and humidity (or moisture) from the air inside a room or building. The air is cooled using a refrigerant.
  2. The blower pushes the chilled air coming off of the evaporator into the ductwork, venting system, or room itself.
  3. Meanwhile, the condenser is heating up coils too, with heat collected from the interior air. The heated releases to join the air outdoors.
  4. Refrigerant moves from the evaporator coils to the condenser coils by use of a compressor pump.
  5. The fan, very similar to the blower, pushes air over the heated condenser and forces this hot air outside of the building. Think of it almost like hot exhaust coming out of a car.
  6. A filter must be in place for an air conditioner to work correctly and long term. The filter removes particulates like dust and pet hair from the air pulled from the interior. This keeps the cooling coils cleaner and working more efficiently for a more extended period.
  7. The thermostat is the control panel for the A/C unit. Sometimes these are mounted on the unit itself, or accessible as a small box separate from the air conditioner (usually for central A/C units).

Types of A/C Units

Window AC units stacked in bedroom on carpet next to the window

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Now that you understand the basics of how an air conditioner works, let's do a quick review over what types of A/C units are out there. Some common problems are specific to the type of unit used.

Central A/C

For houses and buildings that use central air, installation usually takes places during initial construction. They utilize a system of ducts, vents, and registers to move air around a large interior. Original installation can be pricey, but they are a quiet and extremely reliable way to cool your home evenly.

Room Unit

A room A/C unit works well for a single space. Somewhat portable, room air conditioners may mount in an open window. This low-cost option is extremely popular, but not the most efficient as air can leak out of the room if the space around the unit is not sealed from the outside elements.

Ductless or Mini-Split

A mini-split A/C unit works well for spot cooling without ductwork, such as a room unit, but with a much higher price tag. They are energy efficient and also capable of heating, not just cooling. You might see units like this inside large chain hotel rooms.

Evaporative Cooler

Technically not an air conditioner, the evaporative cooler – also known as a swamp cooler – use evaporated water to cool air instead of a refrigerant. The colder air circulates throughout the house. This type of system is more common in regions with very low humidity, like Arizona.

Top A/C Problems

Window air conditioner disassembled for in-depth cleaning on the kitchen table

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Not every problem requires professional help to solve. Waiting on the air conditioner repairman to show up while you sit boiling indoors is more than just an inconvenience – it affects every aspect of your day from sleep and showers to what’s for dinner.

The United States Department of Energy outlined some of the most common air conditioner problems, and we went a step further to include some tips and tricks on how to handle them.


There are several potential leak sources. It may not always be the same cause. Let’s take a look at what the problem may be.


When an air conditioner has run low on refrigerant, it will not work as efficiently, and there is a problem. The refrigerant circulates through a closed system, meaning there is no reason for it to leave the A/C unit. If there is a leak, only a professional technician should make repairs and recharge the system.


Room A/C units are susceptible to improper drainage of water. They require stable, level mounting to work correctly.

Central air conditioners have drains for water that lead outside the building. If the piping has too many kinks or gets clogged, it may cause backflow of water or keep water from draining properly – causing leaks directly around the unit.


Room units mounted in a window may allow air to seem outside. Leaking cold air keeps the unit running unnecessarily and permits humidity to remain in the room. Sealing the space around a wall unit with duct tape (for small gaps) and panels (larger gaps) will solve this problem.

Central air requires a system of ductwork, but if there are too many kinks in the tubes or sections are not sealed properly, you could lose cold air into the attic or crawl spaces around the house. This can happen due to poor installation, but also wear over time might lead to gaps in the ductwork or sealing tape coming loose.

If you have safe access to the ductwork, inspect the system on your own before calling for help. It might mean a simple repair with, yes, duct tape is all you need.

A/C is Running, but Not Cooling

Man installing an air conditioning unit on a room

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Losing the chill can result from a few different things:

  • Improper thermostat setting
  • Sensor moved (Located behind the control panel, the thermostat sensor should be near the evaporator coils, but not touch them. Bend the wire back in place if needed.)
  • Dirt (change the filter, dust off the coils, check the drain)
  • Low refrigerant (call a professional)
  • Compressor issues

Uneven Cooling of Rooms

Blocked vent or registers, damaged ductwork, or poor insulation can all lead to different variant temperatures around the home. If one room is frigid and another a sauna, look at external factors like windows facing the sun or if furniture is obstructing air flow.

Strange Noises

If the A/C squeals when shutting off and on, the blower motor may be wearing out. Adding lubricant to the oil port may help, but if the banging or clanging gets loud, shut off the unit and call the shop.

If you hear clicks when the unit turns on and off, there may be a problem with the relay. If you hear this or rattling noises, contact a professional and schedule a service call.

No clicks or squeaks, but you hear a smacking sound like someone is shuffling a deck of cards inside the A/C? The blower probably has an obstruction of some sort. Shut off the A/C and look inside for any debris. You can also blow out or vacuum the blower blades as a precautionary measure.

Inadequate Maintenance

One of the easiest and most important things you can do to increase the life and efficiency of you’re A/C unit is to change the filter (and use the proper size filter). When the cooling cools become too dirty, the system continues working harder than it should and can lead to premature failure of fans or the compressor.

A/C Problems Tips and Advice

Man Checking the temperature gauges on an aircon for A/C Problems

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If the A/C shuts off unexpectedly, check the thermostat first. When the batteries die, it will cause the entire unit to shut down.

On unusually hot days, the A/C or compressor might reach a high-pressure limit and trip the circuit breaker. Let the unit cool for at least five minutes before resetting any breakers and turning the unit back on. If resetting the unit from your home’s breaker box, check the high-pressure switch located on the compressor's control panel.

When the air conditioner is too big for the space being cooled (central A/C), the system may shut off and on too frequently, leading to electrical malfunctions as the wires and terminals wear out.

Don’t run the A/C with windows and doors open. It negates the hard work your air conditioner is doing!

Pay attention the part of the A/C that is outside. Plants growing too close to the unit can lead to significant problems later.

The coils on an A/C should never freeze. They should be cold to the touch, and maybe even sweat with a little condensation. But if your unit does freeze, turn it off to defrost. Knocking off the ice could damage the coils, release refrigerant or ruin the unit.


Featured Image: CC by 2.0, KOMUnews, via Flickr