Car air conditioning: recharging, cleaning and signs of a fault

How car air conditioning works#

Air conditioning moves heat from inside the car to the outside. A compressor, driven by the engine or, on many electric and hybrid cars, electric, compresses the refrigerant. The refrigerant gives off heat in the condenser, in front of the radiator, and cools the air in the evaporator, hidden in the dashboard. The air then passes through the cabin filter and reaches you.

The same system dries the air: that's why it demists the windows quickly and is useful in winter too. The water collected on the evaporator drains through a pipe under the car.

Signs your air conditioning has a problem#

• It cools weakly or not at all: usually refrigerant is missing because of a leak, but it may also be the compressor, a sensor, a fuse or the condenser fan.
• It cools on the move but not at the lights: possibly the cooling fan or the amount of refrigerant in the system.
• A mouldy or damp smell when you switch it on: bacteria and mould on the evaporator, plus an old cabin filter.
• Weak airflow from the vents, even on full: a clogged cabin filter or a blower problem.
• Noise or clicking when you switch it on: the compressor, its clutch or the drive belt.
• The windows mist up and don't clear quickly with the air conditioning on.
• Water on the front footwell carpet: the evaporator drain is blocked and water gets inside.

An air-con recharge: what it means and when you need one#

Refrigerant (often called "freon" in Romania) isn't used up like oil or fuel. If it needs topping up often, the system is leaking somewhere: a seal, a pipe, a condenser hit by stones. At the garage, a recharge usually means:

1. Recovering the remaining refrigerant with a dedicated station, which also shows how much was left in the system.
2. Vacuuming the system and checking that it holds.
3. Filling with the type and amount of refrigerant the manufacturer specifies, usually on a label under the bonnet, plus compressor oil if needed.
4. Checking the air temperature at the vents with the engine running.

Older and newer cars use different types of refrigerant, which don't mix. The garage needs equipment for the type in your car.

Refrigerant: what the rules say#

The refrigerants in car air conditioning are fluorinated gases, regulated at EU level. Regulation (EU) 2024/573 on fluorinated gases requires the maintenance, repair and refrigerant recovery of car air conditioning to be done by people who hold at least a training attestation. The minimum requirements for that attestation have been set since 2025 by Implementing Regulation (EU) 2025/1893, and each member state organises the training.

• The gas is sold only to the right businesses: for this kind of work, the regulation allows only businesses with certified or trained staff to buy fluorinated gases.
• Non-refillable cylinders for these gases are banned in the EU, empty or full.
• A leaking system isn't refilled until it's repaired: the EU directive on vehicle air conditioning (2006/40/EC) bars garages from filling it if an abnormal amount of refrigerant has leaked out.

Don't try to recharge the air conditioning yourself: you may put in the wrong amount or the wrong type of refrigerant, the gas escapes into the air and the leak stays. Go to an air-conditioning specialist with trained, certified staff.

Cleaning the system and the cabin filter#

Moisture collects on the evaporator, and over time bacteria and mould grow there, hence the unpleasant smell. An air-con clean means cleaning and disinfecting the evaporator and the ducts, with foam, a spray or an ozone or ultrasonic machine, depending on the garage's method, usually together with a new cabin filter.

• The cabin filter is changed at the interval in the service book, sometimes at the routine service; on dusty roads or in the city it may need changing sooner. Some filters also contain activated carbon, which traps smells.
• When to clean it: when the smell appears; many drivers have it done in spring, before the hot season.
• What you can do: a few minutes before you stop, switch off the air conditioning and leave the fan running, so the evaporator dries out.
• In winter, run the air conditioning now and then, unless the manual says otherwise: it demists the windows and keeps the system working.

What to ask the garage#

1. Whether their staff are certified to handle refrigerant and they have equipment for your car's type of refrigerant.
2. How much refrigerant they recovered compared with the manufacturer's figure: if a lot was missing, where the leak is.
3. How they look for the leak: a pressure test, UV dye or a detector, and what needs repairing.
4. What the clean includes and whether they change the cabin filter too.
5. What warranty they give on parts and labour (see what a repair warranty covers).

How CariX helps#

In the free driver account you keep your car and the work done on it in one place.

• Your own reminders: you can add a reminder yourself, for example to have the air conditioning cleaned before summer or to change the cabin filter, and get it by email.
• "Is the price fair?" shows an indicative price range for air-conditioning work in your city, from the prices businesses list on CariX on their pages and quotes; the real price depends on the car and on what's repaired.
• Warranties: if the garage records a warranty on the job line, in months or kilometres, you see it under "Active warranties" on the car and get an email 30 days before it ends (for a warranty in months).
• Costs: log repairs in the car's costs and see what the car costs you each month.