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How to properly use your car's air conditioning during summer months

Posted 10th June 2024

How to properly use your car's air conditioning during summer months

The only thing Brits love more than queuing is talking about the weather. Whether that’s small talk we use as an icebreaker, or to fill an awkward silence, there’s nothing we love more than nattering about the outdoor conditions come rain, wind, or shine. 

And as cliche as it may seem, there is truly nothing more unpredictable than the British weather. For summer 2024, we’ve already been predicted to experience heat waves, yet at the same time, we've been told to expect ‘50 days of rain’, according to the Met Office. 

When the weather chops and changes, it can be pretty frustrating, especially for drivers. When it's hot outside, our cars often take the brunt of it. And when it’s hot AND raining outside, our car windows have a habit of steaming up, leaving us confused about the car's air conditioning solution. 

Even experienced drivers might find themselves unsure of when to use the air recirculation button or whether to continue receiving fresh air from outside the cabin.

To ensure a bit of rain is the only driving inconvenience Brits need to deal with this summer, our car servicing team share some fool-proof examples of exactly how and when to use the internal vs. external car air conditioning functions:

Inside air vs outside air - When to use what

Learning to drive can be stressful enough without remembering the ins and outs of the dashboard, too. And while it might make logical sense to turn our car air conditioning to hot air to heat us and cool air to cool us down, there’s actually another, possibly more important, function that many drivers don’t use correctly: the internal vs. external air functions.

Air Button

When using the internal (or air recirculation) function, your car’s air conditioning system will recirculate the air already inside your vehicle for maximum cooling. When you select the external air function, your car will bring in new air from outside by opening an air duct in the front of your vehicle. 

Here are just a few examples of which function to use for different circumstances:

1. Heatwaves

When driving in summer it’s recommended that you use the internal air recirculation button to stop the cool air escaping and letting the hot air in. Similarly, hayfever sufferers will want to consider using the internal air recirculation buttons to ensure they’re not pulling in pollen particles from outside their vehicles. 

However, if drivers are getting into their cars after it’s sat in the sun for some time, it’s recommended to use the external air function at first to bring new, fresh air in. 

As often reported, the materials inside our cars can become slightly toxic in hot weather conditions. This is because our car interiors are made with chemicals, and sometimes these chemical compounds will be released when our interiors get used (i.e. sitting on the seats or pressing any dashboard buttons). 

When cars are left sitting in the sun, the rate at which these materials release toxins exacerbates, pushing chemicals, such as formaldehyde – a preservative – into the air. If this air isn’t expelled, some drivers could experience mild nausea or headaches as a result, so it’s crucial to get some fresh air into the car before setting off.

2. Rain

The unpredictable British weather means that we’re often driving from tree-splitting sunshine to monsoon-like rain, and this can quickly wreak havoc with our windscreens, causing them to fog up. 

When driving in the rain, drivers should turn on the A/C and click the external air function. They’ll then want to switch their A/C unit to the windscreen function (this symbol is usually three wavy upwards-pointing arrows within a rectangle), triggering the vents at the base of the wind shield to help clear any fog. 

Windscreen Air Setting

Our windscreens fog up when it rains because the warmer air inside the car holds more moisture than the colder air outside. By switching to the external air conditioning function, drivers are allowing the cooler air outside to come in and prevent fogging. 

3. Traffic

Another issue many drivers face during the British summertime is the increased risk of traffic, as people across the country set off on their staycations. 

If drivers find themselves stuck in traffic, it’s recommended that they switch their car air conditioning functions to the internal circulation setting to prevent any exhaust fumes from surrounding cars from entering their vehicle.

4. Motorway driving

Driving on motorways can feel much more tiring than driving on more scenic routes. Driving monotonous roads doesn’t require as much concentration as others, and can often cause drivers to zone out or feel tired. This phenomenon is often dubbed as ‘highway hypnosis’.

To ensure they remain alert when driving on motorways for a significant amount of time, drivers should switch their car air conditioning to the external function. 


The fresh air from outside will help keep oxygen levels in the car high, which can help to combat any tiredness drivers might feel.

5. Smoking or vaping in the car

If drivers or one of their passengers are smoking or vaping inside the car, then they’ll want to turn on the external air circulation to help expel the smoke and keep fresh air entering the vehicle. 

While it’s not illegal to smoke while driving, there are laws against smoking with under-18s in the car. Both the driver and the smoker could be fined (if the driver isn’t the one smoking) for being caught doing this. 

If, however, a driver is caught smoking without children in the car and the police deem it as a distraction, they could still be fined up to £5,000 and receive up to 9 points on their licence.

The air con in my car is not working

If you’ve tried our servicing team’s car air conditioning hacks and find that they’re not working for your car, then you may need a car air conditioning service, repair or recharge. 

Most car manufacturers will advise getting a car air conditioning ‘recharge’ or car air conditioning ‘regas’ every 2 years, but for many people, they leave it longer than that. 

A car air conditioning system runs on refrigerant gas canisters, and over time, the gas will deplete – whether you’re using it frequently or not. If your air con feels warm, or hot, then it’s likely that you need to replace your refrigerant gas canister so the air can run cold again. 

Air Con Temp

Similarly, if you find your car air conditioning is working fine but has an unpleasant smell when you’re using it, then a simple air conditioning cleaning can should do the trick - and will last longer than a standard air freshener.  For an optimal effect, ensure your car air conditioning is turned on full, with all windows and doors closed. Do not sit inside the vehicle while the air con can is decanting.

While there could be other reasons why your car air conditioning isn’t working quite as you’d like it to – especially on a scorching summer day – it’s best to check with a reputable mechanic, and potentially get a car air conditioning service, to get to the root cause of the issue. 

At Dick Lovett, we understand that buying a car is just the start of the journey with your new or approved used vehicle. That’s why, across our range of Dick Lovett dealerships, we provide state-of-the-art servicing and repair facilities, and offer air-conditioning servicing. Get in touch with our team today. 

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