Why is my car aircon blowing hot air?

Periodic car aircon maintenance is essential for Filipino car owners. Thanks to global warming, worldwide temperatures are rising, which means hotter summers from here on end. And since the air-conditioner is a Pinoy motorist’s best friend, tempers flare up quickly when the A/C fails without warning. If your aircon is blowing hot air, it’s a sure sign the system needs cleaning, servicing, or both.

But to fully understand why your aircon is not working correctly, it’s necessary to learn the basics of auto air-conditioning and how it works in cooling the cabin.

How does my car aircon work?

All air-conditioners work on the principles of evaporation, condensation, compression, and expansion. The aircon lowers the temperature by reducing the moisture content in the air. Remember, hot air is moist, while cold air is drier. The aircon in your vehicle absorbs the interior air, lessens or removes moisture from the air, and blows the cooler air through the aircon vents. It does this by cycling refrigerant (or Freon) and converting the Freon from gas to liquid and back.

What are the main parts of a car air-conditioning system?

The A/C in your vehicle consists of five main parts:

1. Compressor

The compressor sucks low-pressure and low-temperature Freon gas and compresses it to produce high-temperature and high-pressure gas. You can find the compressor under the hood and beside the engine. A serpentine belt drives the compressor.

2. Condenser

After compressing the refrigerant gas, it passes to the condenser. The condenser is mounted in front of the radiator and cools the refrigerant while maintaining its high-pressure state. The condenser uses ambient air and fans to cool the refrigerant.

3. Receiver or Dryer

The receiver or dryer removes excess water and moisture from the refrigerant using desiccants or drying agents.

4. Expansion valve

The expansion valve removes pressure from the liquid refrigerant, allowing the Freon to expand and dropping the temperature.

5. Evaporator

When low-pressure Freon passes to the evaporator from the expansion valve, it changes from liquid to gas, producing a cooling effect. The blower fan will push the colder air from the evaporator to the aircon vents. In addition, the low-pressure Freon will vaporize as it absorbs heat from the cabin. The compressor will suck in the low-pressure Freon, and the process repeats continuously.

Why is my car aircon blowing hot air?

Now that you know a thing or two about the main parts of an aircon system, it is easier to diagnose why the system keeps blowing hot air. The possible causes are as follows:

Broken or faulty compressor

If the compressor is old or not working, no amount of refrigerant will cool the system. The compressor is the engine that drives your car’s A/C system, and it’s also the costliest part to replace. If you turn the A/C on, the compressor should come to life. If not, you could be dealing with a broken compressor or faulty wiring.

Inoperable cooling fan

But if the compressor is working and the aircon insists on blowing hot air, the cooling fan is next to check. Depending on the make and model of your vehicle, it can have one or two cooling fans, and most are found directly in front of the condenser. As you turn the A/C on, the compressor and the cooling fan should also turn on.

Leaking refrigerant

The aircon in your car is a sealed system. If the system lacks refrigerant, it indicates a leak. There’s a saying in the HVAC community that “Freon never fades, it just leaks,” so keep this in mind. Of course, if the aircon lacks or is empty of refrigerant, it will fail to cool the interior of your car.

Dirty A/C system

The evaporator can accumulate a large amount of dirt and debris as it absorbs hot air and distributes cold air. It’s the reason why the aircon system should be cleaned and flushed at least once a year to maintain its cooling efficiency.

How often should my car aircon be cleaned?

Do not wait for the aircon to blow hot air before bringing your vehicle for servicing. The aircon in your car should be cleaned and serviced at least once a year or every 20,000 to 30,000 km. Periodic aircon cleaning and maintenance is necessary to prevent more significant problems from cropping up. In addition, a clean A/C system helps you save on gas. When in doubt, read the owner’s manual.