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Why Is My Air Conditioner Not Cooling the House? [Updated for 2023]


Everyone expects their air conditioner to supply cool air.

But sometimes an air conditioner doesn’t hold up its end of the bargain. This is what happens when you don’t properly prepare your air conditioner for summer.

When that happens, you’re left feeling cheated, frustrated, and hot under the collar – literally. You’re not sure if it’s time to repair or replace your air conditioner.

We get a lot of questions about air conditioners. This one is by far one of the most common.

Here’s How It’s Supposed to Work

Normally, your air conditioner circulates refrigerant between the evaporator (inside your home, near your furnace’s air blower) and the condenser (outside your home).

The condenser converts the refrigerant from a gas to a liquid state through a heat exchange process. The heat that is released is dissipated, leaving only cool air to be delivered back into your home.

7 Reasons Your Air Conditioner is Not Cooling Your House

If you’ve got any of these problems, your air conditioner won’t cool your house properly.

1. Your Thermostat is Set Incorrectly

This is the easiest thing to check. It’s also the easiest to fix.

Depending on the kind of thermostat you have, simply setting it to ‘ON’ doesn’t guarantee you’ll get cool air. It could just be causing air to blow in without the air conditioner actually operating.

First, make sure your air conditioner is actually switched on. This can be found in the shut-off box near the air conditioners.

Next, set a temperature 5-6° below your home’s current temperature. You should hear your outdoor unit turn on and see the fan spinning.

After a few minutes, cool air should be issuing from your vents.

If this doesn’t happen, that’s when you call us.

2. The Condenser is Dirty

Your condenser performs the heat exchange process and depends on a fan delivering outdoor air to keep it functioning.

But if your condenser is dirty or clogged, it becomes much harder for your air conditioner to work correctly.

This is another easy solution you can do yourself.

First, do some landscaping around your air conditioner’s condenser: dense vegetation will interfere with heat dissipation, making it harder for your air conditioner to perform properly.

An industry standard is to have approximately 18 inches of clear space on all sides.

The next thing to do is to clean your condenser. This will take longer if you don’t have a protective cover for your condenser.

Use a bucket of water and a gentle soap to wipe away any dirt or grime. Be very careful, particularly around the condenser fins: if they break, you’ll have a whole new problem.

Tip: A cover for your condenser helps protect it from harsh winters, and prevents damage that could cost you a pretty penny. If you don’t have a cover, we strongly recommend you get one.

3. The Air Filter is Clogged

Your furnace’s air handler is what pushes the air from your AC into your home. But first, it has to go through the air filter.

Normally, this is no problem. You get the cool comfort you want, and particulates are trapped in the filter so the air is pure and clean. It’s a win-win.

But an air filter can only hold so much.

If you never change or clean it, clogging is guaranteed to happen. The more clogged it becomes, the less air gets through.

Replacing your air filter is something you can do yourself. If it’s a reusable filter, all it takes is a little soap and water. Remember to let it dry completely before replacing it.

We recommend checking your air filter every 30 days to avoid this problem in the future.

4. There’s a Refrigerant Leak

This is a serious issue that should be handled by professionals.

Refrigerant is what absorbs the heat from the air, and is circulated between the evaporator and the condenser. When there’s not enough refrigerant, your air conditioner can’t cool your home properly.

Refrigerant doesn’t get used up: you should always have the same level. If this level has dropped, you have a leak.

Signs of a refrigerant leak include:

If you suspect you have a refrigerant leak, turn off your AC right away and contact us.

5. There’s a Broken Motor or Compressor

Air conditioners have a lot of moving parts. Sometimes, one or two of those parts will fail.

This can be hard to diagnose if you aren’t a heating and cooling expert. If you suspect a mechanical problem is causing your lack of cool air, Knight offers top-quality Calgary air conditioner repair services >

6. Your Ductwork Has Leaks

Your central air conditioner relies on your ductwork to circulate the air through your home.

But did you know your ductwork could actually be hindering your AC?

It’s true: leaks in your ductwork let that lovely cool air escape before it reaches its destination.

Not only do you stay hot and uncomfortable, but you actually spend more money to reach your desired temperature.

You’ll have to consult a ductwork professional to begin fixing this issue.

7. The Air Conditioner is the Wrong Size for Your Home

This is one of the more expensive problems to have.

Air conditioners keep getting more and more efficient, which means the one you had 10 years ago is not the same as the one you’ll get today. Without using new information to make the right choice, homeowners wind up with a new air conditioner that is too big or too small.

When this happens, your air conditioner will not work correctly. Instead, one of two things will happen:

  1. An undersized air conditioner will have to run constantly to reach your desired temperature – with little chance of success. This takes a lot longer, and it wears out your AC extremely quickly. Think of being on a treadmill for hours at a time, with no breaks. Eventually, you’d collapse. That’s what will happen to your air conditioner.
  2. An oversized air conditioner will short-cycle: turn off and on quickly and repeatedly. The air may feel cool, but it will never be consistent.

Unless you’re willing to replace the air conditioner you just bought, this is a problem that will persist.

If it’s time to install a new air conditioner, we urge you to consult with our Calgary professional AC installation team. They’ll do a thorough inspection, and make sure you get the right size.

Air Conditioner Maintenance is a Must

The best way to fix these problems? Avoid them altogether with annual air conditioner maintenance.

Not only will this make sure you have cool air all year round, but it will actually improve both your air conditioner’s energy efficiency and lifespan.

That means more savings for you! Cue your happy dance.

You could get even more benefits if you become a Knight Preferred Member. You’ll get $200 worth of free maintenance, a discount on repairs, and member-only specials you won’t want to miss.

So don’t wait for when your air conditioner isn’t cooling your house: schedule an appointment with Knight today!