Car Air Conditioning

How car air con works and how to look after it

Car air con isn’t just great for cooling the car down in summer - it also helps to demist windows in winter. But over time, your car’s air conditioning may stop working as well as it used to. 

Regular air conditioning services will keep the cool air blowing and help your car to run efficiently.

Find out how air con works, what can go wrong with it and how to keep it cold.

In this article
Understanding car air con Maintaining your air con Regassing your air con Troubleshooting your air con


Understanding car air con

How does car air conditioning work?

Air conditioning in your car works by using a refrigerant inside the heating and ventilation system to cool the air in the car. It’s powered by your car’s engine, which is why it uses more fuel when you have the AC on.

Here’s how the AC system works:

  1. Compressor - The refrigerant gas changes to liquid under high pressure in the car’s compressor.
  2. Condenser - It travels through a condenser, which looks like a radiator, where the heat evaporates.
  3. Receiver drier - The now-cool liquid refrigerant moves into the receiver drier which removes moisture.
  4. Expansion valve - The liquid passes through the expansion valve which lowers the pressure.
  5. Evaporator - The liquid enters the evaporator where it turns back to gas and absorbs heat, with a fan blowing cool air across the evaporator and into the cabin.
  6. Repeat - The refrigerant gas returns into the system to start the process again.

What’s the difference between air con and climate control?

Climate control is different to AC. Climate control regulates the temperature by automatically adjusting the AC or heating based on the setting you’ve picked. 

When the driver or passenger sets their desired temperature, the system triggers the air con or heating. Once the system has reached the right temperature, it levels off to keep the temperature steady.

It means you don’t have to fiddle around with any dials or turn the air on and off to get the right temperature in the car.

What about AC in electric cars?

The AC in electric vehicles (EVs) can be slightly different to the AC in vehicles with internal combustion engines. The AC pump is electric and is powered by the battery rather than by an engine. It forms part of the high voltage system in an electric vehicle, so any repairs need to be carried out by a trained technician.

Maintaining your air con

How often does air con need to be serviced?

Your car’s air conditioning isn’t included in a standard car service. You’ll either need to add it onto your service for an extra fee or get it checked out separately.

It’s best to get the air con serviced around once every 2 years to keep it running efficiently.

What happens during a car air con service?

The main part of a car service will involve flushing out the old refrigerant and replacing it with new refrigerant (regassing).

The mechanic will also check the system for any leaks or cracks.

What’s the best way to keep air con working?

Don’t be tempted to save your air con for a scorching day. It’s best to use it regularly throughout the year as it can seize up if it’s not used. It’s useful even in winter, when it helps to remove moisture from the air and demist your windows.

As well as using and servicing your air con regularly, make sure you change the cabin filter regularly and get the AC debugged if it smells.

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Regassing your air con

What is air con regassing?

Regassing your car’s AC is the main way to keep it working well.

Over time, the refrigerant gas inside the car’s air conditioning can leak out, making it struggle to cool the air. Regassing the air con means removing the old refrigerant and refilling it with new refrigerant.

Although it’s possible to do this yourself as long as you don't have an electric car, it won’t save you much money or time. It’s best to get an expert to look at it to avoid anything going wrong.

When does the air con need to be regassed?

A mechanic will regas the air con each time the AC is serviced. We recommend getting it done around every 2 years.

Troubleshooting your air con

Why does my car AC smell bad?

Unfortunately, the evaporator in your car’s cooling system can be the perfect place for bacteria, mould and fungi to grow. This can sometimes lead to a horrible musty or “sweaty sock” smell when you turn on the AC.

An air con recharge, where the refrigerant is replaced, won’t fix the problem. Instead, you’ll need to pay for an air con debug which decontaminates the system and kills any bacteria or moulds.

Why is my car AC blowing hot air?

The most common cause of air con blowing out hot air is low refrigerant levels. Over time, the refrigerant can leak out of the system and the AC won’t be able to keep your car cool any more.

The most common way to fix the problem is by regassing the air con. Replacing the refrigerator gas will let the system cool down the air in the cabin and will make your car run more efficiently too. The air con uses more fuel when it struggles to cool the air.

How can I fix my car’s AC?

If the air con in your car isn’t working, it’s best to get it serviced and recharged. Most of the time, regassing the air con will fix the problem.

Sometimes, there might be a bigger problem like a crack in the system which is leaking refrigerant. This is more likely to happen if you don’t use the air con regularly and haven’t had it serviced in a long time.

If you drive an electric vehicle, it’s dangerous to try to fix the air con yourself. It’s part of an EV’s high voltage system, so you’ll need a professional who’s trained on these to look at it for you.

Published: 2 October 2020 | Updated: 2 October 2020 | Author: The AA

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