'Should the rear aircon be running even without passengers?' [Newbie Guide]

Updated Apr 07, 2021 | Same topic: Beginner's Guide

You’re not really saving much by leaving it turned off anyway.

The arrival of the summer months means your car’s air-conditioning gets to be used more frequently. Cars with two seating rows usually have one set of aircon vents located on the dashboard, while vehicles with three rows tend to have an extra set of vents for rear occupants.

Aircon switch

Summer increases both the ambient temperature and your aircon usage

In this pandemic era where most people are encouraged to stay within the relative safety of home, chances are that your vehicle isn’t likely filled to capacity. More often than not, it will just be you behind the wheel, with a solitary front passenger at most.

If you’re not traveling with anyone else, should the rear air-conditioning be turned off?

Where your car’s performance is concerned, the aircon doesn’t add much. In fact, many car owners will argue that this only adds to the engine’s load, since the compressor that increases the refrigerant’s temperature and pressure is powered by a belt attached to the engine.

This explains the long-standing habit of turning off the aircon when a car is about to negotiate an uphill route, to make it easier for the engine to power the vehicle forward. You’ll just have to contend with a sweatier ride.

VW dashboard with aircon

Drivers tend to switch off the aircon to reduce the load on the engine during heavier tasks

In the case of rear air-conditioning, this usually involves a blower spreading cold air that has been routed to the sections behind the front row using ducts.

The longer your rear aircon is unused, the more moisture will accumulate on the piping inside the ducts, providing an excellent breeding ground for fungi and bacteria.

>>> Related: Car aircon refrigerant: How to remove & Replacement cost


Moisture from not using the aircon for a long period of time breeds fungi and bacteria

These undesirable elements will end up getting blown into the cabin the next time you use the aircon after an extended period of non-use. At best, this will result in a persistent moldy smell that not even your air freshener can remove.

At worst, this can pose a serious health issue for occupants who have an allergic reaction to fungus. In some cases, the blower will also end up malfunctioning if it hasn’t been used for a long time.

Second-row vent

Just leave the rear aircon running even if it's at the lowest setting

>>> Related: List of popular car aircon repair shops in the Philippines

If your vehicle has a rear aircon vent, just leave the blower running even if it’s at the lowest fan speed. At the very least, it helps the cabin cool down faster before you drive under the summer heat.

Get your fill of cool automotive tips at Philkotse.com.

Joseph Paolo Estabillo

Joseph Paolo Estabillo


Joseph has been a member of various car clubs since he got his driver's license in 2004 – old enough to remember riding in taxicabs with analog meters, but his fascination with cars goes way back. After nearly two decades of working in broadcast media, he shifted gears by coming on board as Philkotse’s first Filipino member and staff writer in 2017.

Apart from his role in Philkotse as Content Team Lead, Joseph has written episodes for Drive, which has been airing on CNN Philippines for five seasons running. He has also delivered content for various car dealerships based in the U.S., spanning multiple brands such as Alfa Romeo, Maserati, Jeep, Dodge, among others.

Keeping his hopes high and his revs low, he dreams about owning a Kei car when he retires. Hates slow parkers.

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