Car air-conditioning maintenance: why shouldn’t you top up the refrigerant ‘by eye’?
Summer heat or long traffic jams—these are the ultimate tests for your car’s climate control system. However, while some drivers enjoy the cool air inside their cars, others, unfortunately, have to deal with stuffiness, unpleasant odors coming from the vents, or the AC suddenly failing at the most critical moment.
In this article, experts from STS explain why air conditioning maintenance should be performed annually, what the consequences are of refilling the system with refrigerant “by eye,” and why you should only trust a specialized service center with your climate control system.
Technical Nuances of Climate Control: The Complexity of Modern Systems
Most car owners only think about their air conditioning system when it stops cooling. However, a modern car air conditioner isn’t just a “fan blowing cold air,” but a complex, hermetically sealed circuit with high pressure, sensitive electronics, and special compressor oils.
Unlike other automotive fluids, the refrigerant inside the system constantly changes its state—from gas to liquid and back again. If this balance is disrupted, the entire thermodynamic process breaks down: the air conditioner begins to wear out prematurely, the refrigerant boils where it shouldn’t, and instead of the desired coolness, the cabin is filled with stuffy air.
In this system, nothing is trivial: every gram of refrigerant and every drop of lubricant is calculated by engineers at the factory for the specific circuit volume and compressor capacity. Any deviation from the specifications during recharging immediately impairs the climate control system’s performance, and a significant error in dosing can instantly put the compressor out of commission.
Why doesn’t the saying “you can’t spoil porridge with oil” apply to freon?
There’s a common misconception among drivers: “The more freon you add, the better and cooler the air will blow.” In practice, the opposite is true.
Recently, a Peugeot owner came to the STS service center. It’s a common story: the car was serviced at a makeshift shop, where the technician relied on average figures. The fact is that in many French cars (particularly Peugeot models), the exact amount of refrigerant varies significantly depending on the model, engine type, year of manufacture, and trim level. The difference can be as much as 100–200 grams, which is a huge amount for a closed-loop system.
The Peugeot owner’s model was misidentified, and the vehicle was charged with significantly more refrigerant than specified by the manufacturer. In this case, the saying “you can’t spoil porridge with oil” backfired on the owner.
What happens when there is an excess (overdose) of refrigerant?
A rapid rise in pressure: the excess refrigerant does not have time to fully evaporate and enters the compressor in its liquid state.
Decreased cooling efficiency: warm air comes out of the vents instead of cold air, since the pressure in the system exceeds the normal level.
Enormous strain on the compressor: the pump operates at its limit, and the compressor oil loses its properties and is washed away from the friction parts
Risk of hydraulic shock and failure: the compressor is designed to compress only gas. If there is too much refrigerant, it enters the compressor in a liquid state. As a result, the compressor experiences a powerful internal shock (hydraulic shock), which instantly breaks or even ruptures its mechanism.
Activation of the relief valve: at critical pressure (over 25–30 bar), the system vents the excess gas through the relief valve. Along with the high-pressure refrigerant, compressor oil is forced out, splashing onto the drive belts, alternator, and sensors under the hood, leaving the compressor itself without the necessary lubrication.
Seeking help from STS technicians early on saved the air conditioner. Our specialists drained the excess refrigerant, evacuated the system, and recharged it with the exact amount of refrigerant strictly according to the specifications for this model.
Why “refilling from a can on the side of the road near a shopping center” is a trap
As the heat sets in, mobile recharge services pop up in shopping center parking lots and on the side of the road. The temptation to “quickly top off the refrigerant” often results in costly repairs.
Why is unprofessional refilling dangerous?
Recharging “by eye”: The pressure gauge on the can shows the current pressure, which depends on the ambient temperature. It’s impossible to determine the exact weight of the refrigerant in grams using this method.
Lack of vacuuming: Before recharging, air and moisture must be removed from the system. When moisture reacts with the oil, it forms an acid that corrodes the aluminum tubes and the interior of the compressor.
Neglecting compressor oil: When refrigerant leaks from the system, oil escapes as well. By refilling only the gas, you leave the compressor unlubricated.
Questionable refrigerant quality: Cheap refrigerant often contains harmful impurities that can damage seals.
Features of Climate Control in EVs and Hybrids
While in a conventional car with an internal combustion engine, the air conditioner is responsible solely for cooling the cabin, in electric vehicles and hybrids it is the main element of the entire vehicle’s thermal management system. The reason is that the high-voltage battery and electronics operate within a very narrow temperature range. A malfunctioning or improperly charged air conditioning system in an electric vehicle not only leads to a hot cabin but, more importantly, causes the battery to overheat, results in a loss of range, blocks fast charging, and triggers emergency mode for the entire vehicle.
Maintenance of the climate control system in modern EVs has a number of key features:
High-voltage battery cooling: The air conditioning system plays a role in regulating the battery’s temperature. Battery overheating leads to degradation and a reduction in range.
High-voltage electric compressors: Inverter-driven electric compressors operating at 300–400 V+ are used here.
Special dielectric oils: Using conventional lubricant (PAG) instead of dielectric oil (POE) leads to insulation breakdown and a short circuit to the housing.
STS specialists possess the necessary certifications, specialized equipment, and extensive experience servicing climate control systems for Tesla, Nissan Leaf, VAG models with 48V MHEV systems, and other hybrids and electric vehicles.
How to Care for Your Air Conditioner: Tips for Car Owners
Natural refrigerant loss is about 8–15% per year due to micro-pores in rubber hoses and seals. To keep the system in working order and avoid costly repairs, follow a few simple rules:
Turn on the air conditioner in the winter: at least once every 2–3 weeks, run the climate control for 10–15 minutes in a warm parking garage or after the cabin has warmed up. This will allow the compressor oil to lubricate the rubber seals and protect them from drying out and leaking.
Replace the cabin air filter: A clogged filter reduces airflow, puts extra strain on the blower, and promotes bacterial growth.
Make sure to disinfect: regularly treat the evaporator with an antibacterial solution to prevent mold growth and unpleasant odors in the cabin.
Why should maintenance be done annually, and why choose STS?
Preventive measures taken by the driver are important, but they cannot replace a full technical service. That’s why an annual service visit before the start of the hot season is the only way to ensure that the pressure in the circuit is normal and that the compressor is receiving sufficient lubrication.
STS offers a full range of maintenance and repair services for HVAC systems in all types of vehicles. We don’t just refill refrigerant—we provide a comprehensive suite of technical solutions:
Thorough diagnostics and vacuuming: We check the system’s leak tightness, operating pressure, and sensor condition, and remove moisture before every recharge.
Automated and precise recharging: We work with R134a and R1234yf refrigerants strictly in accordance with automakers’ specifications, adding the required amount of compressor oil.
Antibacterial evaporator treatment: Professional disinfection eliminates mold, bacteria, and unpleasant odors, restoring fresh and safe air to the cabin.
Circuit flushing and line repair: We clean the lines of dirt and wear debris, and we thoroughly restore aluminum tubes and rubber hoses of any complexity.
Our own inventory of remanufactured compressors: If your unit can’t be repaired, you won’t have to wait for weeks—we’ll select and install a remanufactured compressor with a warranty right on the spot.
Expertise in working with MHEVs, hybrids, and EVs: We have all the necessary certifications for high-voltage systems and use specialized POE dielectric oils.
Don’t wait until the heat or a sudden climate control failure catches you off guard. Schedule a professional diagnostic check and maintenance for your car’s air conditioning system at STS—trust the comfort and safety of your car to our experts!
