Motoring experts say that many people typically close windows and doors before blasting the air con.
However, this traps hot air inside and slows your car from cooling down, so here is what to do instead.
Drivers warned over air con mistake stopping car from cooling down
Ben Welham, motoring expert at cinch, said: “Once you get in your car, open all the windows to let the warm air out of the cabin.
“You should also turn your air con up to max straight away so it can start cooling down.
“With your air con still turned as cold as it will go, angle the air to the footwell vents.
“This will use the cooler, denser air to push the warm air out of the still open windows, helping the car cool down more quickly.
“Once the air con starts blowing cold and most of the warm air has escaped, close all your windows and turn on the recirculate button.
“This will keep your interior filled with the coolest air, since the air con is only cooling air it has already cooled before.”
For electric or plug-in hybrid cars, pre-conditioning before setting off is recommended.
Drivers are also reminded to carry water, apply suncream, and ensure their air con is properly maintained or regassed if it is not cooling effectively.
The advice comes during a period of extreme heat across the UK.
On the 50th anniversary of the start of the 1976 heatwave, our scientists have explored how similar events could evolve in a warmer climate.
A plausible future scenario shows UK temperatures reaching 45°C by 2056.
Read more:https://t.co/CBaQkm9VSJ pic.twitter.com/BoynONJ9Az
— Met Office (@metoffice) June 23, 2026
An amber weather warning is in place for much of central and southern England as well as part of Wales, from 1am yesterday (June 22) to 11.59pm today (June 23).
A wider amber alert, covering more of Wales and down to the southwest of England, is then in place from midnight in the morning on Wednesday (June 24) to 11.59pm on Thursday (June 25).
During this time, a rare red warning is also in place covering London and the surrounding areas in central England.
The Met Office says that an “exceptional spell of hot and humid weather is expected across this region, with impacts to the general population highly likely”.
How do I know if my car aircon needs regassing?
The first sign that your air con needs regassing is that the air being blown from the vents is not as cool as it used to be, or it doesn’t feel any different when the AC is switched off, the RAC explains.
They add: “If you can’t remember the last time the system was regassed, it’s probably worth doing.”
Getting your air con regassed should cost somewhere between £50 and £200, depending on your system and where you get it done.
Most manufacturers recommend you service your air con every two years or so.
As well as the car being uncomfortable in hot weather, and taking longer to demist the windows in winter, it can also be bad for the car in the long run.
Pipes are likely to crack and parts are likely to seize up if it isn’t used.
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While you can buy air-con regas kits to attempt the job yourself, it is not advised.
Most kits are nearly as expensive as paying a specialist to do the job, and if anything goes wrong, you may be left with an expensive repair bill.
When was the last time you got your air con regassed? Let us know in the comments.
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