Category - Air Conditioning
Guide author photo

Will Scholfield, Engineer

31 Jan : Updated 4 Mar ● 8 min read

Top 5 Common Air Conditioner Problems & How to Fix Them

An air conditioner can be a big investment, and with potentially expensive repair costs, it’s important you understand the signs that something may be wrong with the system if they arise. This way, you can identify faults and get them fixed before they become more serious. 

To help you do this, we compiled the five most common problems that our HVAC technicians encounter when they’re servicing AC units. By the end of this guide, you will be able to spot a problem and understand what to do and the next steps to take. 

Why is my air conditioner not working? 

Across the lifespan of your air conditioning unit, it can experience several problems. The first sign that something’s wrong will often be a drop in the system’s overall quality, whether this means it’s taking longer to reach the desired temperature or that it’s delivering insufficient airflow. 

To avoid these problems worsening, you must know how to tackle them. This will avoid costly repairs and ensure you’re not feeling the heat for too long.

1. Improper use

Our HVAC engineers often find that the reason an air conditioner is struggling to work properly isn’t actually because there’s a mechanical or functional problem.

Air conditioning systems are pretty complicated pieces of kit and need to be used as per the manufacturer’s instructions if they’re to perform correctly. One of the most common examples of misuse and reasons for breakdowns is leaving your windows or doors open whilst the air conditioning unit’s turned on.

If you do this, the air conditioner must work far harder to keep your home cool, as warm air from the outside is entering just as fast as it can be removed. This increased pressure means your system is more likely to fail due to excessive wear. 

How to avoid faults due to improper use

Our engineers’ top tip for ensuring maximum efficiency and longevity is to check that all your windows and doors are closed before turning your air conditioning on. You may also want to close any internal doors, as this will reduce the amount of air space your units need to cool.

If you think you have misused it in the past, get your air conditioning unit serviced by a qualified HVAC technician. They can identify any issues before they become major problems, which could end up saving you money in the long run.

2. Lack of maintenance

Over time, your AC unit may start to clog up with dust and debris that has been sucked into the system from the air. Even though you’ll have filters and fans installed to rid your system of these materials, they must be thoroughly cleaned regularly to make sure the system itself remains clear.

If your air conditioner does get clogged, it can cause more problems further down the line, so you must frequently check the unit for dirt and debris and carry out subsequent cleaning and maintenance.

How to maintain your air conditioning unit

Firstly, it makes sense to clean your unit thoroughly twice a year (or more frequently if you feel like it isn't performing as it should). We've covered how to clean your air conditioning unit in our air conditioning maintenance guide.

With this being said, there's nothing quite like a professional clean to optimise performance. This cleaning can be carried out as part of your air conditioner’s servicing, so make sure yours is booked in just before the summer months to guarantee a cool breeze when you need it most.

Filters on an air conditioning system should be changed every 1-2 months for optimum performance or more frequently if you have any pets or rely heavily on your air conditioning system. If you have a reusable filter, it needs to be cleaned just as frequently.

Our engineers’ top tip is to plan your air conditioning unit’s annual service well in advance. Just like boiler engineers get booked up in the winter months, HVAC engineers are busiest in summer, so you may struggle to get an appointment at short notice.

3. Leaks from the system

There are two main reasons that your air conditioner could be running low on refrigerant; the first is that insufficient refrigerant was added to the system during the installation process, and the second is that there is a leak somewhere in the system. 

It can be straightforward for a qualified HVAC technician to identify and fix an air conditioning leak, but the leak may go unnoticed for some time unless you know the symptoms. These include: 

  • The system not blowing cool air
  • The indoor unit being noisier than usual
  • An increase in your electricity bills 

How to fix a leak in your air conditioning system

If you have a leak, simply adding more refrigerant won’t solve the problem. Over time, this will leak out of the system, and you’ll find yourself right back at square one. Instead, a trained HVAC engineer should add a fluorescent dye to the refrigerant system to identify the leak's exact point. Once identified, the engineer can seal the leak, and you’ll be cooled down in no time.

The refrigerant levels should match the recommendations in the manufacturer’s instructions, so use this as a guide to determine if there is a leak in the system. Leaks should be dealt with as soon as they arise, as they can damage the environment and others who come into contact with the refrigerant.

If you suspect there is a leak in your air conditioning system, don’t put off getting it fixed. Contact an engineer immediately to investigate and rectify the problem before it worsens.

4. Drainage issues

Issues around the drainage of your air conditioning must be sorted quickly to avoid a breakdown in your system. 

Drainage problems can happen for a few different reasons. For example, if the air conditioning units aren’t mounted level on your walls, your system won’t be able to drain properly, which could cause internal flooding.

Typical symptoms of drainage problems include musty or mouldy smells or signs of water damage, like dampness, near your indoor unit. 

How to fix drainage issues

It’s worth routinely checking the unit’s drain to ensure it isn’t clogged and that waste liquids can drain away with no problem. If you feel like your system isn't draining properly, you'll need to call an HVAC professional to service your unit.

5. Faulty thermostat sensors

Home air conditioners have a thermostat sensor to manage the temperature and avoid overuse once your home is lovely and cool. If a sensor’s position shifts for any reason, it may affect its ability to read the ambient temperature accurately, causing the system to function incorrectly.

How to fix faulty thermostat sensors

You should take care not to alter the position of the thermostat once it is installed. If you do knock or move it accidentally, don’t panic! These things happen sometimes, and a dislodged thermostat shouldn’t cause major issues if readjusted promptly.

If you find that your sensor is malfunctioning, it may be because something’s blocking it. To fix this problem, remove the cover of the sensor and clean the parts inside using a soft-bristled brush. If the problem persists, it's best to call an expert HVAC engineer to take a look.

How to fix air conditioner problems

If you’re noticing some air conditioner problems, here are some quick scenarios and fixes you can do yourself to prolong the life of your units.

Have you got a dirty filter?

If a dirty or clogged filter is restricting the airflow within your system and preventing it from effectively cooling the air into your home, you should clean or change the filter as soon as possible.

As a rule of thumb, we recommend you change the air filter in your unit at least every 1-2 months unless the filter is reusable. This is especially important in warmer weather, as you’ll likely be using your air conditioning system more frequently. Or, if you use both the cooling and heating functions of the system (which can be an effective solution for smaller properties), you may find you need to replace the filter more regularly.

Take a look at our blog for further tips on how to test and improve the indoor air quality in your home.

Is there a warm airflow?

Blowing out hot air when it should be cool is one of the more common air conditioner problems. There are a number of reasons why this could be, including electrical issues, clogging in the system or an issue with the compressor.

Are your thermostat settings correct?

If your thermostat isn’t functioning or giving you the correct air temperature, you should check your thermostat settings. 

Programmable thermostats allow you to easily control your air conditioning temperatures or schedule your air temperature via a mobile app, even when you’re not home.

As mentioned previously, it’s also important to ensure your sensors haven’t been knocked or moved for any reason.

Explore how you can control your home's temperature straight from your phone with our ultimate guide to smart thermostats.

Fix your air conditioner problems as soon as they arise

Catching issues while they’re small can prevent them from becoming much bigger and more expensive to rectify. 

For more information on how to maintain your system, check out our dedicated air conditioning guides

Alternatively, you can discover how to install a new evaporator coil in your air conditioner or our Samsung air conditioning fault codes & solutions for specific advice.

Beat the heat

Beat the heat

Sleep well every night with our fixed price air conditioning packages.

Get your fixed price now