So, you’ve decided to prepare for the summer heat? Brilliant! Having no AC on a hot summer’s day is absolute torture. You can avoid this sweaty situation by taking action early and maintaining your car’s AC system.
If you’ve noticed that the air coming from your AC vents isn’t as chilly as you’d like for it to be, you might be wondering if it’s time for a recharge. But how often does car AC actually need to be recharged?
In this article, we’ll take a look at the cars AC system; learn how it works, possible faults, the reason behind them, and find out how often your car AC needs to be recharged.
How the Car’s AC System Works
Your car’s AC system is very similar to the AC in your home and office. It uses a special refrigerant gas to provide cool air. The AC system serves four functions:
- Cooling of the inside air
- Circulating the cooled air
- Purifying the air
- Dehumidifying the air
By performing these functions, the AC system maintains passenger comfort, in which case the average person feels most comfortable with an ambient temperature ranging from 70°F (21°C) to 79°F (26°C), with a relative humidity range of 45 to 50%. If the temperature of anything goes below or above this range, we think of it as HOT or COLD. To achieve this, the car’s AC system uses various components to fine-tune the air temperature and distribution.
Now, here’s the main working principle of air conditioning:
All refrigeration systems work by exploiting the properties of gases. If you compress the gas its temperature rises, if you decompress the gas its temperature drops.
- You take a gas, that’s at room temperature, and you compress it.
- The gas gets warmer.
- Now, you allow the gas to cool back down to room temperature while still being compressed.
- Then, you decompress the gas, which is already at room temperature.
- The gas cools down BELOW room temperature.
Now what you have is a gas in a pipe, that is cold. What if you put a fan in front of the pipe? The fan starts blowing COOL AIR because the air that is moving around the cold pipe gets cooled down. This is how an air conditioner works.
But wait, don’t forget that at the start of the cycle, we compressed the gas, which in turn made it hotter. We also need to cool down the hot compressed gas into room temperature. For this, we use another fan, which will cool the hot compressed gas back to room temperature. This is the most difficult part of the process and it’s the reason that air conditioner units pump such huge amounts of hot air into the atmosphere.
Here’s How The AC System of a Car Works in Better Detail:
The system uses a special refrigerant gas R134a and is divided into the high-pressure side and the low-pressure side.
Low-pressure R134a refrigerant vapor enters the compressor and gets compressed into high pressure and high-temperature R134a vapor. The vapor that also contains special lubricant oil is circulated into the condenser (the radiator at the front of your car). As the high temperature and high-pressure vapor travels through the condenser, the heat is released into the much cooler ambient air. While the vapor is cooling down and passing through the condenser tubes, it condenses into a liquid (hence the name – condenser). This high temperature and high-pressure liquid travels through the filter drier and onto the small orifice of the expansion valve. This valve provides a restriction against which the compressor pushes.
When the liquid refrigerant passes through the expansion valve, its pressure lowers and so does its temperature. Now it’s a low pressure and low-temperature vapor. Next, the refrigerant passes through the evaporator. The hot air of the cabin is being blown through the evaporator, thus cooling the air of the cabin down. Then, the R134a refrigerant is pulled back into the compressor and the cycle begins again.
How Often Does Car AC Need to Be Recharged?
Here’s the thing, while the amount (weight) of the refrigerant should be checked periodically – there are no set intervals for an AC recharge. This means your car AC may never need to be recharged. Even though an extremely small amount of refrigerant could escape into the atmosphere in some AC systems occasionally, such tiny amounts probably won’t affect your car’s AC systems cooling performance, because it’s an insignificant amount. Therefore if you’ve noticed that the AC system isn’t as cold as before, you probably have a leak.
Fixes You Can Do Right Away
First, try cleaning or changing the cabin air filter (located under the glove box in most cars).
Cleaning the filter is FREE and will improve the cooling considerably. The cabin air filter is often overlooked as a contributor to poor AC performance, but it shouldn’t be. It is designed to stop dust, pollen, and other particles from entering the cabin, purifying the air which the driver and passengers breathe. When the filter gets clogged up, airflow to the cabin decreases, meaning less air flowing through the ice-cold evaporator, thus reduced cooling of the cabin air.
If that was not enough, you can recharge the AC system yourself using a DIY kit but, depending on the size of the leak, the refrigerant will escape the AC system after some time. A DIY kit will likely get your AC topped off and running for the whole summer (assuming the leak is small).
There is no need to get your car AC recharged if the AC system works fine. The refrigerant in your car doesn’t degrade over time (assuming there are no leaks in the system). The best (and only) indicator that you DO need to recharge the AC system is when the system begins to cool less than it used to.
Please, DON’T use any AC “stop leak” products. They contain nasty chemicals that will not only stop the leak but gum up your whole AC system. You will risk damage to the whole system. We’re talking thousands upon thousands of dollars in repairs to replace the whole AC system. Seriously, it’s not worth it!
In case you’re unsure if your cars AC system is cooling properly, here is a table of the temperature levels you should expect from your car’s AC system:
|Temperature inside the cabin||20 oC, 68 oF||25 oC, 77 oF||30 oC, 86 oF||35 oC, 95 oF|
|Temperature inside the AC vents oC||6-8||8-10||8-12||9-14|
|Temperature inside the AC vents oF||43-47||43-50||43-54||48-57|
How AC Leaks Form
Leaks mainly form due to oxidation of the aluminum parts of the AC system. The most vulnerable part of the AC system is the condenser, which is located at the front of the car. Because the condenser is located at the front of the car it’s susceptible to damage from rocks, road salts, and moisture. Oxidation is especially common in places that are poorly vented and covered.
Other Common AC Faults and the Reason Behind Them
- Poor cooling performance – poor airflow through the condenser and the evaporator; faulty pressure sensor; faulty cooling fan; engine overheated.
- Not enough refrigerant in the system: either 30-35% too much refrigerant or 70-75% too low; poor vacuum; plugged evaporator.
- Faulty expansion valve – stuck mechanical parts of the valve; plugged valve.
- Faulty valve in the compressor – valve plugged with contaminants.
- Faulty AC compressor clutch – not enough refrigerant; faulty clutch relay; incorrect clutch air gap.
- Restriction in the system – contaminants plugging up the system.
- Ice in the evaporator – faulty thermostat; faulty fan; faulty compressor valve.
- Faulty compressor – bent valves inside the compressor; plugged compressor.
- Hot air out of the AC vents – leaking or stuck air mix vents; leaking evaporator.
Can You Fix AC Leaks by Yourself?
Unless the AC system is absolutely empty of R134a refrigerant, NO! You would have to recover the R134a refrigerant before attempting any leak repairs. Not only is releasing refrigerants into the atmosphere dangerous for your health it is also ILLEGAL. Refrigerants are ozone-depleting substances, damaged ozone layer results in increased levels of sunburn and skin cancer.
Get the System Checked by Your Mechanic
In the end, there is no getting away from it – you will need a mechanic to check the system for leaks eventually. The mechanic will first verify the complaint and locate the leak using UV light since the refrigerant contains UV dye. After the required components are replaced, your AC system will be refiled with the required amount of r134a, lubricating oil, and UV dye and you will be free to enjoy the feeling of a freshly serviced AC system!
You’ve probably heard that you should periodically have your evaporator cleaned and disinfected but how do you prevent the bad odor in the first place?
Simple! Before the end of your drive, turn off the AC and crank your blower motor up for 15 minutes. This will dry it out and make it difficult for the bacteria on your car’s evaporator to start a musty party.
If your already too late and your AC smells funky, you can use an evaporator cleaner to kill the bacteria and mildew.
Eddie is the co-founder of CarCareCamp.com, and the site’s primary contributor. Automotive repair has played a major role in his family for generations and he’s determined to continue the legacy further on. Under his belt, Eddie has a bachelor’s degree in Automotive Electronics Engineering and almost a decade of experience working as an electrician in a major semi-truck dealership in Europe.