Most cars come with air conditioning nowadays, it is an extremely convenient luxury to have, even in the UK! After having A/C, being in a car without it on a hot day can almost seem unbearable. So here’s our guide on how to look after your air con system.

How air conditioning works

Air conditioning systems use a refrigerant in a sealed system to remove heat from the air inside the cabin. They do this by strategically compressing and decompressing the fluid in conjunction with heat exchangers inside and outside.

The fans in the climate control system blow filtered air across the internal heat exchanger, known as the condenser, to pump cold air into the car. A cabin air filter is used to prevent pollen and other contaminants being blown into the vehicle.

Things to check when using your air conditioning

These are especially important if you have not used the system for a long time:

Check the temperature of both vents

Naturally the AC should be blowing cold air when active, this should be around 5 degrees celsius. Both sides of the car should receive the same temperature air, if not this could indicate a fault with the ducting system.

Be aware of odours

The inside of the air vents can become the ideal location for mould to grow if not used through the winter months. When using your air conditioning, if any musty or foul smells are present, turn it off and ventilate the car’s interior.

Another cause for unusual odours can be leaking refrigerant, which can be harmful to humans. If you are unsure, many garages can offer A/C checks free of charge, and the systems can be cleaned using a special gas.

Check the cabin filter has been replaced recently

Most cabin air filters are rated for between 20,000 and 30,000 miles. If you cannot see that this has been replaced in your service history, it is advisable to replace this.

An old filter may harbour mould or dirt and cause smells or contaminants to the air. It will also restrict the flow of air into the car. The filters are relatively inexpensive and should not take long to fit.

Air conditioning or climate control?

The terms are often used interchangeably, but there are differences.

Air conditioning is simply the system that cools air within a space, climate control uses a thermostat to monitor the inside of the car. It then uses a combination of heating and cooling to regulate the interior temperature.

Common problems with air conditioning

Because there are many different parts and processes involved in your air conditioning system, it may sometimes need minor repairs to keep it running right.

Leaking refrigerant

As mentioned earlier, the system should be a sealed one. There are however a few common failure points that can allow the gas or liquid to escape.

The most common areas are the condenser, and compressor. The first has very small fins to increase airflow, but these are susceptible to knocks or damage causing a very small leak.

A compressor requires many high pressure internal seals to do its job. These can break down over time and allow the refrigerant to pass through.

To fix this, the leaking component needs to be identified, and replaced. The system will then need re-gassing.

Failed compressor

The compressor, like any pump, has seals and rotating components. Over time these can wear and will eventually fail. This can either cause the refrigerant gas to escape, or to simply stop the air conditioning from working properly.

Mould in the ducting

As discussed, the ducting that directs the air to the vents can be the perfect area for bacteria to grow if the system is not used regularly. If your air vents expel an acrid or foul smell, it could be this that is the problem.

Many garages offering air-conditioning servicing can run a gas through the system to clean and deodorise.

Air conditioning regassing

This is a common job undertaken by garages, whereby the sealed system is re-pressurised with refrigerant.

The method through which the old gas can leak has been discussed above, but these issues should be eradicated before regassing. It is a criminal offence to knowingly vent air-con refrigerant into the atmosphere.

As with system cleaning, most garages can perform a leak test. This is done by pressurising the system with a liquid that glows when exposed to UV light. The aircon is turned on, and any leaks can be identified when inspected with a UV torch.

Can I regas my air-con at home?

There are kits available to buy that allow you to re-gas your aircon at home. The large downside to these is that they often don’t allow you to first check for leaks. It’s possible that the old gas has slowly leaked out over the life of the car, and there are no faults.

With a newer car though, or if your air-conditioning has stopped working all of a sudden, it is unwise to buy a DIY refill kit. For one, it may be a waste of money without testing for leaks, and two, they usually cost only slightly less than a professional refill at a garage.

How to make the most of your car’s A/C system

Keep your windows shut

When driving on a hot day, the windows may seem like the best way to cool off, but this is actually working against the car’s air conditioning system.

With the windows open, warm air is entering the car, this actually increases the cars internal temperature and starts an endless battle between the A/C system and the outside air.

The only exception to this is returning to a hot car, because cars have a lot of windows, the interior temperature can increase way beyond outdoor temperatures, especially in summer.

If the car is swelteringly hot upon starting your journey, open all windows and leave the A/C off for a few minutes. Then switch on the air conditioning and shut the windows, the car will be cool in no time.


It might sound counter-intuitive, but when your windscreen is foggy on a cold morning, the air conditioning is the best way to clear this. It’s due to the system removing moisture from the air, instead of blowing moist air from inside the cabin, or outside the car.

So if your car’s air conditioning is not efficient, smells funny or simply doesn’t work, use these tips to help bring the temperature down.

Or Call AutoCool now FREE on 0800 772 3070 or email us on:

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