SA Road Tests

Your car’s air conditioner: Friend or enemy?

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Posted: October 2018

Practically every modern car has air conditioning. It cools interiors in summer and defrosts windscreens in winter. It’s wonderful. But like most friendly helpers it can, if neglected or abused, turn nasty, make you sick or cause you harm.

First, let’s deal with a popular misconception; air conditioners do not make incoming air cold. They remove heat – there’s a subtle difference - just as your domestic refrigerator does. That can be a mammoth task when your car has been parked in direct sunlight for an hour or more in summer. The temperature inside could be as high as 60-degrees Celsius. You know that because you have read the horror stories about babies and pets left to suffer in unventilated cars.

Most people’s first reaction on entering is to switch the control to “recirc,” aim the ventilators directly at their faces and crank the cooling down to “sub-arctic”. That does three things: It keeps the furnace blasting by recirculating all that hot air until the equipment can eventually catch up. It overloads the system by asking too much of it. And it makes you sick. We’ll get to that later.

A better bet is to keep the aircon off, select the through-flow setting and drive with windows open for a while until the hot air escapes. Once back to almost bearable close the windows, switch the unit back on and set it to your normal, comfortable temperature. Recirculation may be used briefly to speed the cooling process but should be switched off as soon as possible because second-hand air becomes unhealthy.

Aircon units also remove moisture. That's for two reasons; ice crystals formed from residual water could jam the system while humidity causes fogging and physical discomfort. But air that’s too dry is not good for you. Apart from scratchy eyes and burning noses, too little moisture causes dehydration that leads to drowsiness, slower reaction times and muscle cramps.

Stay hydrated and keep the chilly blast out of your face – turn the ventilation vanes upward to direct airflow overhead, along the roof and down to the rear compartment. Your passengers will appreciate it and make them less likely to demand that you turn it down colder still.

Some units also filter incoming air to remove dust and pollen spores. Like all purifiers, these get blocked if used for too long, so replace them at your car manufacturer’s recommended intervals. Trapped allergens could eventually break free and cause the discomfort you hoped to avoid in the first place, while complete or partial blockage can restrict air getting through and thereby overload the fan motors.

Another thing that can clog up and become less effective is the radiator that cools the heat exchanger that in turn chills your surroundings. Put clumsily, this performs an “exchange” by passing warm, but progressively cooling with each cycle, cabin air across an evaporator coil that’s chilled by means of expanding gas. Leaves, bugs and dirt can block the radiator’s cooling fins and stop it working properly. Rather like your swimming pool filter, a quick “back-wash” with a hosepipe will remove debris and return it to full efficiency.

Unfortunately, on some really hot day, you will find that the incoming air simply isn’t getting cold. Provided everything else is in order, it’s probably because the refrigeration part of the system has stopped working. If you’re lucky it will be because refrigerant gas has escaped via imperfect metal-on-metal seals and your local aircon person can top it up for a few hundred Rand. Other possibilities include a broken compressor drive belt or a simple electrical fault.

If you are less fortunate though, one of the rubber tubes carrying gas from point to point will have perished and sprung a leak. A qualified technician can make up a replacement or your franchised dealer might have the genuine factory part in stock – sometimes cheaper. Always check. Alternatively the unit’s moisture remover (called a receiver-drier) could be overloaded and blocked.

Finally, should Lady Luck abandon you completely, the compressor unit that circulates and recompresses the gas could fail and cost big money to replace. Fortunately that usually only happens after quite a few years.

As with anything else, a well-treated air conditioner will provide long and faithful service. Abusing its friendship can cause it to treat you poorly.



Comments or questions?

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