Repairing aircon systems
Air-conditioning is often misunderstood and can be expensive to fix; Rob Marshall gives an overview of the system and details how far a DIYER can go with diagnostics and repairs.
Air-conditioning in your car is often misunderstood and can be expensive to fix. We find out what can go wrong.
Fitted only to more opulent models not so long ago, air-conditioning has become virtually ubiquitous. Should you be in the market for even a used ‘cheapy’, the chances are that your chosen car will possess aircon either as a standalone feature, or as part of a more sophisticated climate control system. The problem with airconditioning overall is that many typical car owners take it for granted and are unaware that the system needs to be maintained to work effectively. Complete failures, however, can be complex to diagnose and mega-expensive to rectify.
Why is air-conditioning important?
While separate to the heater, airconditioning works in conjunction with it to create and maintain an optimum cabin environment. In most cases (certain hybrid and electric vehicles excepted), the engine needs to be running for the air-conditioning to operate. However, the vehicle’s speed doesn't influence its effectiveness, although some systems take speed and throttle position into account and react accordingly, such as deactivating the airconditioning under hard acceleration to direct maximum power to the wheels.
In the UK’S temperate climate, many drivers do not appreciate that airconditioning dries and cleans the air.
For this reason, it is common for the air-conditioning not to be switched on until the summer, due to the operator not being aware that the system performs a useful demisting purpose when called upon. This feature is useful especially in damp weather conditions.
The refrigerant – what is it?
Common vehicle aircon refrigerants are environmentally harmful. This is why legislation prohibits any person from discharging an air-conditioning system on purpose, without having a means of storing the old refrigerant for safe disposal. Apart from being illegal, doing so can also be dangerous.
The Freon R12 designated refrigerant was the earliest popular type, which stopped being used on new cars in the early 1990s and was banned completely by 2001. Should you own a classic, or ‘youngtimer' model, you might look into having the system converted to the commonest R134a, which has a global warming potential of 1300 times higher than carbon dioxide, compared to R12’s 8000 times rating.
After encountering reluctance from Mercedes-benz, which was concerned about its flammability, new cars that were sold in the UK from 2013 replaced R134a with R1234yf, the trade name for which is Solstice. Being only four times more harmful than carbon dioxide, environmental benefits were the main reasons for its introduction. Latest developments have led to carbon dioxide (R744) serving as a refrigerant, which features in several current executive models, such as Audi’s A8 and the Mercedes-benz E-class and S-class ranges. A disadvantage is that the CO2 system needs 7-10 times higher pressures than older circuits and specialist knowledge for their maintenance and repair.
Even so, anybody handling automotive air-conditioning refrigerants must be both trained and certified under the European F-gas regulations, which will continue to be followed in the UK postbrexit, according to DEFRA. While you can still buy R134a canisters for DIY gas top-ups, they tend to be expensive and it is a pointless and illegal task to pressurise a known leaking system with refrigerant. You could also harm the circuit, because you risk potential overcharging and adding
atmospheric air. Professional re-gassing services, where all old refrigerant is removed and stored, the system vacuumed of all moisture, pressure checked and refilled with new refrigerant, will cost a little more but represents far better value – and the work will be guaranteed.
Choose to have your re-gassing and servicing work performed at a reputable garage. This advice has become more critical in the last few years. Due to
the environmental damage that R134a causes, the EU has restricted refrigerant sales, to a volume that declines every year. Unsurprisingly, this has not only increased prices but also means that smuggled refrigerants has become a notable problem. Aside from financing the criminal underworld, the rogue gas canisters can contain virtually anything.
The situation has become so acute that one refrigerant supplier has admitted
to the trade press that it believes up to 20% of the European refrigerant market constitutes smuggled product. Therefore, should you be offered a suspiciously low-priced recharge service, justified by a source of ‘cheap gas’, be suspicious.
Looking to the future, R134a prices will rise before the EU bans it entirely. CM understands that R134a alternatives are being considered but no viable technical solution has been found yet.