Should you turn your A/C off before turning off your car?

A lot of interesting questions come up when you own a vehicle. Perhaps you heard something from an old mechanic or a trusted mentor gave you some automotive advice. But is any of it true? One thing you may have heard is that you need to make sure to turn off your car’s air conditioning before switching off the engine. Below, we’ll dig a little deeper into that piece of advice and the reasoning behind it.

In short, no, you do not have to turn your air conditioning off before turning off your vehicle. That being said, it never hurts to disable electrical systems, including the fan, before switching off the ignition.


How have car air conditioning systems changed through the years?

You may be asking yourself, “Where did this piece of advice come from?” Well, the answer is a bit complicated. Though most components of a vehicle’s HVAC system have stayed the same for several years, other vehicle systems have changed quite a bit. For instance, when engines were carburetors and certain elements weren’t as efficient as they are today, the A/C compressor would place a hefty load on the engine when the system was running. Therefore, by turning off your air conditioning before turning off your vehicle, the A/C would not be on when you started your vehicle back up. Lessening the load put on the carburetor, even just a little bit, made a big difference in terms of emissions when turning on the engine. Another piece of advice that is connected to this age-old issue is letting your engine warm up before driving in cold temperatures.

Using A/C in modern vehicles

As mentioned earlier, modern vehicle systems and engine components have been updated to be more efficient. That allows us to, for example, keep the air conditioner on when we switch off our car. That is especially helpful on hot days when you want your car to cool off as quickly as possible. Not to mention, most remote start features automatically apply the vehicle’s current settings, so you’ll want to have your air conditioning on for that!

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If you have any questions about automotive advice or tips you’ve received, feel free to get in touch with our service professionals right here at Toyota Vacaville.