Why does my car's air con turn on by itself?

I'm afraid I don't follow your advice of leaving the air conditioning on all the time, as surely this will use more fuel?

The air conditioning works perfectly well when turned on, but occasionally it turns itself on when not required, without the air conditioning light going on to show that it is on. I experienced the same problem with a courtesy car I once had. What is causing the problem?

Asked on 5 September 2022 by Christine Lay

Answered by Dan Powell
Using the air con will increase fuel consumption, but keeping it switched off for long periods will also result in potential problems with the AC system. You may be fine using it once or twice a week, but drivers who switch the AC for two or three months at a time will find that the system will no longer operate as it should. This is why I recommend keeping it switched on 100 per cent of the time.

In regards to the AC switching itself on/off, this could be part of the auto setting on your car's ventilation system. The AC may also automatically switch on when you set the fans to demist the front screen. In rare cases, it's a fault with the air con, but I wouldn't be concerned unless the AC was working when the fans were switched off.
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