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A faulty air conditioning system is the last thing you want to deal with when summer arrives.

Read on for:

• The most common air conditioning problems UK homeowners face

• Practical troubleshooting tips

• When it’s time to call in a professional

Six common issues with air conditioning

Troubleshooting air conditioning problems early on could mean you save on hefty repair bills.

From leaky refrigerant to strange noises, it's good to know what to do for each problem.

First up in our air conditioning fault-finding rundown, why is my air conditioner not turning on?

1. Air conditioner is not turning on

It can be a headache if your air conditioning system doesn't turn on. But don't panic just yet.

Here are some things to try before calling in an air con engineer:

Checklist of things to try

1. Check the thermostat

• Replace the batteries if they’re dead

• Make sure the thermostat is set to cooling mode

• Set the temperature lower than the current room temperature

• If the thermostat still isn’t working, it's time to get it replaced by an engineer

2. Inspect the air filter

• Check for dust and debris buildup, which can restrict airflow and cause the unit to freeze up

• Clean or replace the filter if needed (remember to use filters specific to your unit)

• Most filters should be changed every 1–2 months

3. Reset the AC unit

• Press the reset button if your system has one

• Alternatively, switch the thermostat off for 5–10 minutes before restarting the unit

4. Check the circuit breaker

• See if the breaker has accidentally tripped

• Switch it back to the ON position if needed

• If the breaker keeps tripping, contact an AC expert

5. Look for ice buildup

• Check for ice forming on or inside the unit

• Turn the system off and allow the ice to fully defrost

• Ongoing ice buildup may indicate airflow or refrigerant issues

• Contact an air conditioning company if the problem continues

Contact a local air conditioning engineer for help and advice

Finding experienced air conditioning engineers near you is simple using Checkatrade's free mobile app.

Or read on for other common issues with air conditioning and what to do about them.

On Checkatrade, you'll only find trades who meet our high standards and pass up to 12 checks.

2. Air conditioner not blowing cold air but running

There are several reasons why your air conditioner unit might be running but not getting cold

Thermostat issues

One of the most common reasons why an air conditioner system might be running but not cooling a house is due to thermostat issues.

Low refrigerant levels

Refrigerant is the substance that your AC unit uses to cool the air. So, if there’s not enough of it, your air conditioning won’t be able to function correctly.

But here's the thing to know: home air con systems are closed loops. So if the refrigerant is low, it indicates a leak.

Dirty air filters

Air filters are designed to trap dust and dirt and prevent them from circulating around your home.

Over time, however, they can clog with debris, making it more difficult for cool air to circulate and increasing energy consumption.

Faulty condenser or evaporator coils

The condenser coil is responsible for removing heat from the refrigerant. Meanwhile, the evaporator coil is responsible for cooling the air.

If these coils are dirty or damaged, your air conditioner may run but not cool your house. This is because the coils cannot transfer heat and cool the air effectively.

Wrong size of AC unit

An oversized unit can be too powerful for your home and lead to short cycling. In turn, the unit will turn on and off frequently, increasing wear and tear and decreasing efficiency.

On the other hand, an undersized unit may struggle to cool your home effectively - especially during hot days and heat waves.

3. Air conditioner is leaking

There's nothing more annoying than a dripping AC unit. A blocked filter, clogged condensation line or damaged pipes are often the culprits

For more information about the causes, check out our expert advice guide on why is my air con dripping.

4. Air conditioner is freezing up

One of the reasons your AC unit may not be working properly is that it keeps freezing up.

Freezing can be seen within the evaporator coil, or on the exterior of the outside unit (the condenser coils). You might see a thin layer of ice due to frost having built up on the refrigerant lines.

5. Air conditioner making strange noises

An air conditioner can make different noises depending on the type of problem - from hissing caused by a refrigerant leak to a banging sound because of a loose component.

These noises often indicate it's time to repair or replace your unit.

For more information about the causes, check out our expert advice guide on why is my air conditioner making strange noises.

6. Air conditioning fault finding

Many modern air conditioning systems, including models from Mitsubishi Electric, Toshiba, Samsung, and Hitachi, display fault codes when there’s a problem with the system.

These codes can point to issues such as low refrigerant, blocked airflow or electrical faults.

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Want to find out more about air conditioning repairs? From how much an air con service will cost, to how to find the best air conditioning engineer, we're here to help.

FAQs

What does an air conditioning unit service consist of?

An air conditioning service will consist of a thorough clean of the system's components, such as the filters, coil, fan, and drain pan.

It's a good idea to get your air conditioning system serviced regularly to keep it in good working order, once any repairs have been carried out.

How often should a home air conditioner be serviced?

Conditions vary greatly between industrial buildings, offices, and residential properties. Each situation will need to be evaluated individually. Generally speaking, we recommend getting it checked at least once per year.

Is it worth getting air conditioning serviced?

Yes. Regular servicing can improve efficiency, reduce breakdowns and help extend the lifespan of your air conditioning system. Most units should be serviced annually.

How much does it cost to service an air conditioner?

Air con maintenance will cost around £30 - £60 per hour for the labour, plus the cost of any refrigerant required. This can cost between £35 - £130.

How much does it cost to install air conditioning?

Take a look at our air conditioning cost guide for information on costs.

Can a problem with the radiator affect the air conditioning?

Yes. In some systems, overheating or poor airflow can affect air conditioning performance and reduce cooling efficiency.

What is the 20-degree rule for air conditioning?

The 20-degree rule suggests your AC should cool indoor temperatures to around 20°F (11°C) lower than the temperature outside. Setting the thermostat too low can overwork the system.

Is it legal to install air conditioning in the UK?

Yes, air conditioning is legal in the UK. However, installation must comply with building and F-Gas regulations, so it’s best to use a qualified engineer.

Worked your way through the air conditioning units problem-solving tips above, and still no luck? A checked and reviewed air conditioning engineer near you can help.

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