Car air conditioning regas/re-charge and maintenance

In any car refrigeration system, excess heat is transported from the passenger compartment to the environment, and the key components involved are the air conditioning compressor, the condenser, and the circulating refrigerant. Up until a few years ago, an HFC, or hydrofluorocarbon (usually one named R134a) was the refrigerant mostly used in mobile air conditioning systems, it having replaced a much nastier number called R12, back in the late nineties.

HOW ITWORKS

As we now know, these fluorinated chemicals can do huge damage to the environment and, since around 2013, less damaging refrigerants, primarily one called R1234yf, have become obligatory for use in new cars. Some high-end models from Mercedes-Benz and Audi, for example, have recently adopted different climate control systems that use carbon dioxide, or R744 as a refrigerant. They have to work at higher pressures, cost more, and use more energy, which may seem counterproductive. They have also been troublesome, but there may be a long-term trend to CO2 systems, as on purely ecological grounds the greenhouse gas effect of CO2 is massively lower (1,400 times lower!) than that of any kind of fluorocarbon refrigerant.

In the meantime, nearly all recent cars use R1234yf refrigerant, and this generally needs a top-up, or full gas recharge every two-to-four years, as the refrigerant slowly escapes to the atmosphere at a rate of around 10 to 20% per cent a year. We might add at this point that there's much to be gained by operating your air conditioning system all year round, as this helps the various seals in the system stay soft and lubricated, without which they tend to lose more gas. Window demisting is usually more effective with the air conditioning turned on, although it's best to get the heater warmed up first before turning the ‘AC’ button on, if you have a manual system. Most climate control systems will do that automatically.

So, either as a routine check, yearly or biennially, and preferably before the air conditioning performance significantly drops, leaving the system struggling to cool the car quickly, you need a check over of the system before the hot weather arrives. Along with any refrigerant top-up, if required, what is often termed an “Anti Bac Clean” is an extra service that will help avoid a long-term build-up of nasties in the airflow system that can produce musty smells. Replacement of the cabin filter that removes particulates and other noxious components from the climate control intake air might be another good move, although it's often included as part of the regular servicing programme.

The re-gassing is quite a slow process, and garages use special automated machines. You can buy air-con re-gassing kits if you do fancy attempting the job yourself, but we would not really advise it, as the kits are almost as expensive as paying a specialist to do the job. If anything goes wrong, you may be left with a costly repair bill, and there's a risk of polluting the atmosphere if you let any refrigerant escape. Specialists will also have a better idea of how to check for leaks and other problems with any air conditioning system There are safety issues to be considered too, and if the refrigerant gas comes into contact with your skin or eyes, it can cause painful freeze burns.

Regarding costs, most older cars using the R134a refrigerant will probably cost around £60 for re-gassing. More recent cars using R1234yf will cost £100 or more, without any extras like an anti bac clean (£20 to £30), a typical figure being around £120 to £150, which may come as something of a shock. But it should not arise more than once every few years, unless you have a refrigerant leak, and you will likely be charged less if the system only requires a small top-up. Expect the job to normally take around 60 to 90 minutes, and therefore a two-or-three coffee cup stay in the waiting room, which hopefully will be fully air-conditioned!