Why Does My Car AC Feel Humid?

Humidity – the moisture content in the air is a common phenomenon, even inside automobiles. Excessive or consistent humidity can make driving and trips worse. Unfortunately, car’s air conditioning system can increase humidity, well, sometimes. But the question is, “Why does my car AC feel humid?”

Generally, a car’s AC system works by using refrigerant between a liquid and a gaseous state. It absorbs heat and humidity and releases cool, dry air. Sometimes, the system may fail to remove extreme moisture from the interior even after working at its fullest. In such situations, you will feel AC feeling humid.

Of course, high humidity impacts both comfort and the system’s longevity. In a vehicle, humidity can manifest in several ways. You may notice foggy windows, musty smells, damp seats and carpeting, or even visible mold or mildew in severe cases. Over time, moisture can penetrate metal parts of your vehicle and damage them.

Humidity & Its Impact in Cars

I mean, why should you think about humidity? Is it necessary to care about AC feeling humid in a car?

You may experience physical discomfort or aesthetic issues. In general, the air conditioner must remove the warm and humid air. But when things are opposite, you may not like to stay in the car.

Besides, when moisture due to humidity enters the parts of a vehicle, it can be a matter of spending money unnecessarily. It is because high humidity can cause moisture buildup inside the car. And this moisture causes rust on the car battery, chrome, paint, and other components.

Let’s talk about humidity’s impact on AC performance. In this case, I am referring to consistently high humidity, whether it is due to AC or other reasons. Excessive humidity makes the system work more and more. So, it reduces the efficiency of the air conditioning.

Another important thing is that you may experience a decrease in fuel economy. Notably, during short trips, it can be costly as the AC system works harder to cool the vehicle.

The Reasons Behind a Humid Car AC

Humidity within a car’s air conditioning system can be attributed to various factors. Here’s a breakdown of the possible reasons:

Inadequate Cooling

The typical air conditioning system of any vehicle always works to reduce the humidity of interior air. But if your car’s device is not cooling as it should, it may increase the humidity. Reasons behind this can be a malfunctioning compressor, faulty condenser, or a damaged cooling fan (1).

Low Refrigerant Levels

I guess you know about refrigerants, right? It absorbs heat and reduces moisture in the air while you keep the AC on. However, when its level runs low, it cannot provide a bone-chilling environment. Instead, you will start feeling bad due to the humid air (2).

Sometimes, leakage in the system may reduce the refrigerant levels. However, too-low refrigerant levels can cause frosting and freezing at the cooling coil. It may lead to compressor motor damage due to overheating (3). Also, low refrigerant levels can cause the compressor to kick on and off rapidly (4).

Blocked or Dirty evaporator coil

In vehicle AC, the evaporator coil absorbs heat from the interior. It is usually like a frosty haven for heat and moisture. Dust, pollen, and even rogue French fries can build up and make it dirty, blocked, or clogged. As a result, it restricts the free flow of air. The result? Well, it can’t function correctly and causes a humid car interior (1).

Some symptoms of a blocked evaporator coil are weak or no cold air bowing, frost accumulation on it, a strange or sweet aroma, and inconsistent air temperature (5,6,7).

Malfunctioning Expansion Valve

The valve controls the amount of refrigerant going into the evaporator. If it’s malfunctioning, it can also gift you a humid car interior (2). Some symptoms of a faulty component are warm air blowing instead of cold, worse performance than usual, and high pressure in the system. Again, a defective valve may allow contaminants to enter the AC system and cause further damage (8).

Clogged Drain Tube

Another possible reason why your car AC feels humid is the clogged drain tube. Hence, this tube removes condensation from the evaporator coil.

Now, imagine a leaky faucet, except instead of water, it has condensation from your AC unit. That’s what happens when the drain tube gets clogged with leaves, debris, and sometimes tiny insects. When this happens, the condensation that collects in the AC system cannot properly drain. As a result, you can find water leaking inside the car and increased humidity (9).

Mold or Mildews

Mold or mildews, wherever you get them, can create nasty impacts on our health. If you smell something odd, that typically means one thing: mold. And where there’s mold, there’s likely water where it shouldn’t be.

Usually, moisture often facilitates the growth of mold and mildew. They can be exacerbated by a clogged cabin air filter (10). If you have mistakenly spilled liquid or food juice inside the car, they may produce mold inside the car.

Sensor malfunction

Have you checked all the sensors in the AC system, OK? If they are malfunctioning, they may cause the system to operate incorrectly. Therefore, you will feel humid in the car.

External Factors

Sometimes, the humidity malfunctions aren’t even hiding inside your car. And let’s not forget about wet passengers, soggy gym bags, and the occasional spilled smoothie – they all can change the interior environment of your car.

How to Identify a Humid Car AC

You may try to identify some symptoms that may indicate excessive moisture in your car. Some of these symptoms are:

Nasty Odor

Can you smell any foul odor coming from the air conditioning of your vehicle? It may indicate the presence of mold, bacteria, or mildew in the system.

High Humidity/Foggy Windows

Do your car windows fog up when you start driving it? It may happen due to water leaking from the AC and vaporizing into the cabin.

Poor Cooling or Airflow

Is the AC system cooling as good as it should? Suppose the airflow appears restricted (like it’s failing to cool). In that case, it can be a sign of condensation or water collecting in the ducts.

Frozen Evaporator Coil

The AC system may become frozen due to too much moisture. In such situations, the coil freezes up and resists airflow.

Solutions to Troubleshoot Humidity in Car AC

Why does my car AC feel humid? If you want to solve this problem, you can consider a few fixes by yourself or with the help of a professional mechanic.

Treating Inadequate Cooling

Usually, a malfunctioning compressor or a faulty condenser may reduce the cooling capacity of a car’s AC system. In this case, I suggest you replace the components. Well, you may not do it yourself. So, it’s a professional task.

Refilling Refrigerant Levels

It is also a pro job! If you mess with refrigerant (it’s actually delicate matter), it may make things worse. So, contact a qualified technician to refill the refrigerant of the right type and quantity. One more thing: you should ask him to identify and repair any leakage in the system.

Cleaning the Evaporator Coil

You can clean this component with a proper cleaning kit. For example, use a vacuum cleaner gently to eliminate the things blocking the coil. In some cases, you can call a professional vehicle mechanic.

Fixing the Expansion Valve

You may need to repair or replace the malfunctioning expansion valve. After that, it will start functioning again, and there will be no humid feeling inside the car. For the fixes, take expert help.

Deblocking the Drain Tube

If you love do-it-yourself (DIY) jobs, you can perform this solution. Take cleaning stuff from your garage and start removing the leaves, debris, and other materials. However, if the clog runs deep, calling in a mechanic may be necessary.

Removing Mold or Mildew

Say no to liquid spillage! You must clean the mold or mildew quickly if the liquid or moisture produces mold. In this case, I suggest you use special cleaning agents or disassemble the AC parts for thorough cleaning.

Repairing Sensor Malfunctions

Inspect the sensors to see if they are working well. If they are malfunctioning, they may need to be repaired or replaced.

Addressing External Factors

Be mindful of external moisture sources. For instance, you may need to dry out wet seats or carpets. Again, air out the car regularly and dry off passengers and cargo. You may use moisture absorbers to keep the dampness at bay.

Final Words

Do you still think, “Why does my car AC feel humid?” unanswered? For sure, I have explained all possible reasons and their solutions in this blog post. Most of them are easy to follow, aren’t they?

Keep the things dry inside. Also, make sure the AC and its components are working top-notch to remove hot weather and keep the interior humid-free. The last suggestion would be to maintain your car’s health regularly.

Thanks for reading this post till now!

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