Tips and Advice

Car air-conditioning and how to keep it working

We explain why car air-con can fail and discuss how best to fix it

Once you've experienced a car with air-conditioning, it's hard to do without it. While it naturally earns its keep in the summer months, where it chills the interior air and staves off humidity, it can be just as indispensable during colder times of the year. An effective air-conditioning system helps keep your windows clear of condensation, maximising visibility no matter what the outside temperature.

As many drivers will have experienced, though, keeping your air-conditioning system in good health isn't always easy, and can be expensive. Not only can its performance deteriorate over time, but its component parts can be fragile and susceptible to accidental damage. Damaged components can allow the refrigerant gas – the life-force of the system's cooling ability – to leak out, reducing your air-conditioning's effectiveness.

If your air-con no longer cools your car's interior effectively, it almost certainly needs to be regassed – which means replacing the refrigerant gas that does all the work of chilling your interior, as well as lubricating the system's moving parts. However, the first thing to consider is why the gas needs replacing in the first place.

Read on for the pros and cons of a DIY air-con recharge against paying for a professional repair.

Why doesn't my air-conditioning work?

The air-conditioning system in your car works in exactly the same way as the fridge in your kitchen. Both machines use a compressor to pump refrigerant gas around a network of fine tubes, but your fridge probably sits in a safe location where its complicated cooling mechanism is hidden out of harm's way.

Unfortunately, the same isn't always the case with the air-conditioning system in your car. A key part of it, the condenser, works in a similar way to your car's radiator. It has to be positioned where it's exposed to cooling air as it rushes under the front of the car. Unfortunately, this means it can be rather prone to stone chips and impact damage. It doesn't take much force to rupture the surface of a condenser, allowing gas to escape.

There are plenty of other places this essential gas can leak from, too. Over time, seals in the system can grow brittle and porous, hoses can split and and stress fractures can develop in metal tubing.

Can I regas my air-conditioning myself?

There are various DIY air-conditioning regas products available from popular high-street car accessory shops and online suppliers. They usually take the form of a pressurised can of refrigerant gas with a connecting hose and valve through which the gas is transferred into your car's system after you release a control knob. In theory, using such a product is a very straightforward procedure. However, there are many reasons we don't recommend you do, not least the strong possibility that you won't save money in the long term.

Although a DIY air-conditioning regas canister can be cheap, unless you know that your car's system is leak-free, there's no guarantee that it'll restore your air-conditioning to working order. If it leaks, even a fully charged system can lose its effectiveness over a matter of hours. An expert can leak-test your air-conditioning system for a small fee and will also regas for not a lot more money.

Another important consideration is that if you charge a leaky – or 'open' – air-conditioning system, you're effectively discharging refrigerant directly into the atmosphere. This is an illegal act of pollution under the Environmental Protection Act 1990 and could land you with a hefty fine.

Why should I employ an air-conditioning specialist?

With air-conditioning becoming almost universally fitted in new cars, an ever-increasing list of garages, service centres and independent specialists offer car air-conditioning repair. Many have prominent signs advertising an air-conditioning regas for as little as £50 – just twice the cost of many DIY kits, but with a good deal more reassurance. A professional regas is a fast operation and you can often be back in your car within the hour.

Any qualified air-conditioning specialist will have the necessary kit to properly recharge your air-conditioning system. They'll know the precise amount of refrigerant required by your specific system and will also introduce the right amount of lubricant along with the gas – vital for preserving moving compressor parts and keeping seals moist and effective.

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They'll also be able to safely – and legally – evacuate any remaining refrigerant gas from the system prior to recharging it. This isn't something you can do at home – if your system is fully charged but the refrigerant content is too low to be effective, the system will need to be discharged. This should only be attempted with the correct equipment.

Helpfully, most professional specialists will introduce an ultraviolet reactive dye before regassing the system. If your air-conditioning has a leak, the dye will help you see exactly where it is, making it easy to decide whether to effect a permanent repair.

Finally, with competition becoming ever-more intense, there are specialists out there who offer a "no improvement, no charge" service, which really is hard to argue against. Overall, the peace of mind implicit in trusting your air-conditioning to the services of a professional far outweigh any cost saving in attempting the job yourself.

For more information about all aspects of buying, running and driving your car, explore our Buying Advice guides.

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