We look at how to keep your car’s air-con in top working order…
These days, air-conditioning is standard on practically all vehicles and, on a boiling day, it is one of life’s great pleasures to feel a welcome blast of ice-cold air from the vents. To find out how you can ensure proper operation of your vehicle’s air-con, we spoke to expert Helmut Rübler from refrigeration and repair specialist, Alaska Enterprises.
How an air-con works
As indicated in the illustration below, an air-con operates in a closed system with a refrigerant as the working fluid. This means that the incoming hot air never actually touches the refrigerant, but is cooled indirectly by an evaporator (or radiator) in the airstream.
In short, the compressor is powered by the engine’s auxiliary belt and compresses the refrigerant gas that now heats up above atmospheric temperatures. The hot, compressed refrigerant is then passed through the condenser, where the excess heat is expelled and the gas condenses (liquefies) and passes through the fluid container. The liquid refrigerant then evaporates through the expansion valve, cooling the gas dramatically and passing through the evaporator in the climate-control system’s airstream, cooling the incoming air. The refrigerant now continues back to the compressor, where the whole process starts again.
What can go wrong
According to Rübler, a car’s air-con should provide ice-cold relief within five minutes (depending on ambient conditions) and it is best to evaluate this with the back of your hand. If the air is not cold by then, immediately switch off the air-con and get the system inspected.
There are many things that can go wrong with this system, including gas leaks and failure of bearings and seals, as well blockages in the pipes or sensor failures. You can take some comfort in the fact that the last component to fail is likely to be the expensive compressor itself (they cost up to R25 000 apiece). A lack of lubrication is the main reason an air-con compressor fails. During installation, about 150 ml of oil is added to the refrigerant circuit to lubricate the components. When the gas leaks out, so does the oil and the lubrication qualities are lost, leading to failure.
Air-con care
To prevent expensive breakdowns, it is important to run your vehicle’s air-con for at least 30 minutes a week. This action lubricates the system and prevents the bearings on the compressor from corroding at the touching surfaces.
To avoid air-con odours, change the pollen filter regularly, because fungus that grows on the evaporator can cause bad smells. You should also service the air-con once a year. It usually costs about R700 and is a minimal outlay compared with a compressor replacement. A full service can take more than an hour and involves:
• Extracting all the gas from the system and weighing it. This is compared with specification and can indicate if a leak is present. The gas is purified and used again.
• Cleaning the pipes.
• Sucking a vacuum in the system to remove moisture that can cause corrosion.
• Replacing or adding lubrication oil.
• Inspecting the auxiliary belt.
• Rechecking the system afterwards and measuring to see that all related pressures and temperatures are within specification.
Proper air-con operation
When a vehicle is parked in the sun, the cabin air is usually hotter than the ambient temperature. First open all windows and switch fan speed to maximum to expel this hot air. Then close the windows and allow the air-con to do its job. When the cabin air is cooler than the ambient temperature, the process can be sped up by employing the recirculation function to recycle the cabin air until the cockpit is at the desired temperature.
Refrigerants
Prior to 1994, R-12 gas was used as the refrigerant in air-con systems, but it was eventually banned due to environmental reasons. Today, most systems use R-134a, which is more environmentally friendly, although the downside is that the molecules are smaller and the gas can more easily find a way out. According to A-Gas South Africa, the next refrigerant that will replace R-123a is HFO1234yf, which will require a change in servicing equipment and additional training for air-con technicians. It is illegal to vent any refrigerant into the atmosphere and the material must be recycled.
Thank you to Helmut Rübler from Alaska Enterprises (tel 021 697 1335/083 309 2903).
Author: Nicol Louw
