Why is My Air Conditioner Not Cooling My House?

Written by: Paul Cathro

Updated on: December 27, 2022

We explain how to troubleshoot problems with your air conditioning unit. Not cooling? Follow these steps to diagnose the issue.

close up of an air conditioner

There is nothing more frustrating than an air conditioner not blowing cold air when you need it to!

Many air conditioning faults are easy to fix for homeowners. Before you waste your money on repair bills or even getting an entirely new system, try and diagnose the fault yourself and see if there's anything you can do.

Check out these common AC issues and see if you can help or if your problem needs to be handled by a professional.

Common AC Problems & Solutions

There comes a time when most AC units struggle to get the job done the way you expect.

If you notice that your home is not as cool as it once was or if there is a strange sound coming from your unit, then take some time to check out your machine for signs of common problems.

Here's a checklist of common AC problems.

1. Faulty Condenser Fan Motor

If your fan motor is not working correctly then the outdoor unit can't disperse heat, leaving you suffering from an air conditioner that can't blow cold air.

You will find that when you are expecting cool air, you will notice lukewarm air instead and possibly a new noise that you haven't heard before coming from the central unit.

Unfortunately, there is no easy fix for a broken fan, and you will need to call out the professionals to fix this.

Make sure you get in touch with someone that has experience fixing broken AC fans, and you'll soon have cool air circulating.

2. Thermostat is Set Incorrectly

If you keep finding the AC not cooling the house, then it's a good idea to check which setting your AC is on.

If you have it turned to 'On' then you have selected to run the fan all day and night, even when the air is not being cooled down.

This, in turn, can leave you noticing the air changing temp from cold to lukewarm.

The good news is that it is a straightforward fix that you can do for yourself; switch it to Auto and let the machine control when the fan runs.

This will result in cool air when you need it and less energy being used to have the fan on constantly.

3. The Wrong Sized Unit

Many people notice that their AC unit is working and producing cold air but that it is not getting to every room in the house, leaving some rooms sweltering and others just right.

The reality of this situation is that your AC unit is just not big enough to cover your home fully and will need to be replaced.

Sadly this is an expensive problem to solve, and you will need to get hold of a professional AC company.

They will double-check the size AC unit you require and then upgrade your system to get what you need.

Be warned; many companies claim that they can install AC units for low prices but then cut corners to increase their profits (one of these corners being the size of machine they install).

Therefore, always go to a reputable company that may charge more but will also provide a quality service that you can depend on.

4. Compressor Issues

The compressor is central to your AC working correctly and is the main part of the entire system.

When it is faulty, you will notice the AC not blowing cold air around as it did before, and your house will not be cool during high temperatures.

Unfortunately, if this breaks, then you will not only need a professional, but you will need to replace the whole outside unit.

Before you spend a lot of money doing that, make sure that the system isn't still under warranty as this could be the save that you need!

5. Clogged Filter

If you find your air conditioner not cooling, then it is worth checking the air filter for a build-up of dust and fluff.

If a filter is dirty, then it can stop the AC from pumping cool air into the home, leaving you with lukewarm air circulating when you need cool air.

It’s a simple fix; remove the filter and wipe it down until all the build-up is removed, you can use a dry or damp cloth to do this, and the fluff can be composted in a home compost bin. Replace the filter and enjoy the cold air once again.

We explain in more detail how to clean AC filters in our dedicated guide.

6. Leaking Ducts

With any AC unit, there are air ducts that send cool air and take warm air out, but these ducts can spring leaks as the years go by, making the system less useful than before.

You may notice some rooms feeling warmer than others or see less cool air being pumped in.

The only way to resolve this issue is to get a professional in to check your pipes for leaks and then repair any that are found. It’s well worth it as the difference will be noticeable and you can enjoy cool air again.


7. Refrigerant Problems

If you find yourself asking ‘why is my air conditioner not cooling the house?' then it could be due to low refrigerant liquid or a leak.

If your AC system is showing a leak, then you will notice things like a bubbling noise, ice building up on the unit, or the AC not cooling your home.

A refrigerant leak can cause significant damage to the system, and it is imperative that you shut the system down until you can get a professional out to fix it.

If you continue to run your system with leaking refrigerant, then you run the risk of it breaking your compressor.

In this guide, we explain how to check if your AC unit needs a Freon refill.

8. Grubby Outside Unit

Lots of us forget that for an AC unit to work well that the outside part needs to be gleaming too!

When an AC unit has been outside for some time, then it can collect dirt and debris that needs to be removed.

Some of the signs that tell us the unit needs cleaning are lukewarm air circulating and the condenser struggling to function.

The fix is simple; take a hose and gently spray it down until the debris becomes dislodged.

Do not be tempted to use high-pressure jets or a jet washing machine on it as this can damage the component parts, resulting in damage that will need to be fixed by a professional.

9. Old AC System

If your AC has seen better days, it may start to reduce its output and slow down. There are some obvious signs of an air conditioner that is past its best. Look out for tell-tale signals such as the air not getting as cold as it once did, slowed fans, and lots of minor issues that need fixing.

The fix is simple but expensive; it's time to upgrade your system to a new one that can pump the cold air you require all day long.

Whilst replacing a system is expensive, it can help you cut back on running costs, and so you will eventually make your money back via your utility bills.

10. Outside Temperature

If none of the previous fixes seem right for your problem, then stop and check the temperature outside.

The reason for this is that most AC units are only built to provide enough cool air up to a fixed temperature.

Why don’t you try our suggested fix; if it is a particularly hot day then try using your current AC system along with a ceiling fan to help disperse the cool air around and keep you cool.

The moving air will feel cooler in the room, and you will soon be more comfortable.


It’s clear to see that many air conditioning issues are incredibly easy to fix with the right tools and understanding.

You must take all the necessary precautions before you start to ensure your safety is a priority and never try to fix something that only an HVAC professional should fix.

Regular servicing will help to keep your machine in excellent condition and, in turn, lasting longer.

When it comes to engaging a professional, make sure you have checked their references and certifications before you let them through the door.

Getting the right person to fix your AC is a priority, and sometimes this can mean paying slightly more to ensure the job is done correctly.

Credible professionals will happily share their credentials and references, so you should never feel embarrassed when asking to see them. If you aren't happy with what you see, then engage a different person.

The next time you find your AC not cooling properly, take five minutes to consult our guide and then take steps to get it fixed so that you don't have to live with a system that isn't meeting your needs.

There is nothing better than relaxing in a cool house when the weather outside is too hot to handle.

About the Author Paul Cathro

Paul is an ex-HVAC engineer with 5 years 'in the trade'.

He acquired tinyhousehugeideas.com in 2022 and aims to make it the internet's most comprehensive HVAC resource for small homes in the next few years.

You can learn more about Paul's story here.

Browse his published work on the website here.

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