How do I cool a car down quickly?

Nearly everyone does this in the wrong order: get in, close the doors, switch the air conditioning to maximum on recirculate, and sit in an oven for five minutes while it slowly improves. The reason it is slow is that recirculate means the system is cooling the same superheated air over and over. Get that air out of the car first and the whole thing takes a fraction of the time.

Safety

Step by step

1. Flush the hot air out before you get in.Open the doors — ideally two on opposite sides, or one door and the boot — and let the trapped superheated air escape. Thirty seconds makes a substantial difference. If you are in a hurry, opening and closing one door several times fans air through the cabin surprisingly effectively.
2. Start with fresh air, not recirculate.Set the climate control to draw outside air, with the fan high and the temperature at its coldest. Outside air on a hot day is considerably cooler than the air inside the car, so the system is starting from a lower temperature and pushing the hot air out rather than reprocessing it.
3. Drive with the windows open for the first minute.Moving air is far more effective at clearing a hot cabin than any fan. Windows down for the first thirty seconds to a minute of driving, with the blower running, empties the car of hot air almost completely.
4. Then close up and switch to recirculate.This is the order that matters. Once the cabin air is roughly at outdoor temperature, close the windows and switch to recirculate. Now the system is cooling already-cooled air rather than fighting the outside temperature, and it gets genuinely cold quickly and stays that way.
5. Aim the vents upward.Cold air falls. Vents aimed up push cold air across the roof of the cabin, from where it sinks through the whole space. Vents aimed at your face cool your face and leave the rest of the car warm.
6. Use the windscreen shade every time.It is the difference between a dashboard you cannot touch and one you can. It takes seconds, reduces the peak interior temperature substantially, and protects the dashboard from cracking and fading over the years.
7. Park to think about where the sun will be.Facing away from the afternoon sun, or parking so the windscreen is shaded later in the day, is free. Under a tree is better still, accepting sap and bird mess as the trade.
8. Check the air conditioning is actually working.If the air never gets genuinely cold after all this, the system has a problem rather than the technique. Air conditioning loses refrigerant slowly over years and eventually stops cooling — that has its own guide, and it is not a domestic repair.
9. Do not use a remote start to pre-cool unattended.Where a car has remote start it is fine to use it as designed. Leaving an engine idling unattended on a public road to cool the cabin is an offence and a theft risk, and it is far less effective than the flush-and-drive method.

Tips

• The single biggest gain is the first thirty seconds with the doors open. Everything else is refinement.
• Cracking the windows a centimetre while parked reduces the peak a little, and it compromises security. It does not make the car safe for anything heat-sensitive.
• A cheap reflective shade for the windscreen plus stick-on sunshades for rear side windows makes a noticeable difference for a car that carries children.
• Air conditioning increases fuel consumption slightly at speed, and open windows increase drag. At motorway speeds the air conditioning is usually the more efficient choice, and around town open windows are fine.
• Run the air conditioning for a few minutes at least once a month all year round. It keeps the seals lubricated and the system healthy, and it is the cheapest maintenance the system gets.

Common mistakes

• Getting in, closing up and going straight to recirculate — The system then cools the superheated cabin air repeatedly instead of replacing it. Flushing first and using fresh air until the cabin is near outdoor temperature is dramatically faster.
• Leaving the vents pointed at your face — Cold air falls, so vents aimed upward cool the whole cabin. Aiming them at yourself cools you and leaves the car hot.
• Setting off before the wheel is touchable — A steering wheel or buckle in direct sun can be hot enough to burn, and it is a real hazard when strapping in a child. Flush the car and let the surfaces cool first.
• Never using a windscreen shade — It takes seconds, substantially lowers the peak interior temperature, and protects the dashboard from years of ultraviolet damage.

Questions people ask