How to Remove Moisture from Car AC System?

Moisture in a car AC system has several effects, such as a decline in cooling efficiency, a musty smell, and even costly AC system damage. That’s why understanding how to remove moisture from car AC system is necessary.

Moisture builds up in a vehicle’s AC system for several reasons. In this article, I will guide you through some common reasons for this occurrence and the solution you need to eliminate the moisture from your air conditioner.

So, remove all distractions to enable you to absorb every information in this post.

moisture removal system

How to Remove Moisture from Car AC System

Enduring moisture in a car AC system can be very challenging because the effects are pretty obvious, especially the nasty smell that comes from the presence of bacteria in the system.

Therefore, it is vital to find a way to eliminate the moisture in your vehicle’s AC before the problem escalates. Irrespective of the symptoms you’re already experiencing due to moisture in your AC, here’s how to remove moisture from the air conditioning system.

Use a dehumidifier

Using a dehumidifier is a strategic way of eliminating moisture from your car’s AC system. Vehicle dehumidifier will help you clear off foggy windows, absorb moisture, and prevent the occurrence of condensation. Humidifier is an effective moisture removal system.

Refill refrigerant

If you discover that your car is running low on refrigerant, ensure to refill as soon as possible. This will help sustain the evaporator’s efficiency and disallow the formation of moisture.

Fix the leaks

If you have moisture in your AC, take a moment to carefully inspect the system to ascertain whether or not there are leaks in the air conditioning system. You can use a refrigerant leaks detector.

So, to get moisture out of a car, whatever leaks you spot in any part of the AC, fix them with a sealant or replace the component if necessary.

Replace the AC compressor

Lastly, the compressor plays a vital role in the overall efficiency of the AC system. If you notice that a bad compressor is responsible for the moisture in your car’s air conditioning system, kindly replace the component according to specification.

Ensure to ascertain the type and size of the compressor compatible with your car’s AC before opting for a replacement. Meanwhile, the reality of your budget should be addressed because the cost of replacing an AC compressor varies.

Causes of Moisture in Car AC System

Eliminating moisture from your car’s air conditioning system starts with identifying the exact cause of the problem. Here, I will show you some common reasons why you have moisture in your vehicle’s AC system.

Low Refrigerant

The air conditioning system is designed to work efficiently and circulate cool air when a specific level of refrigerant is present. Running the AC on a low refrigerant level can cause a decline in the evaporator’s efficiency, thereby collecting more moisture.

Low refrigerant levels can also cause the coils to freeze, leading to an overflow and leak in the condensate drain pan. When this occurs, the vents will most likely blow hot air.

Condensation of water vapor 

Excessive condensation on the evaporator is another reason for moisture in a car’s air conditioning system. As the refrigerant passes through the AC system, it absorbs heat and moisture from the circulated air inside the vehicle.

However, when the cooled refrigerant goes below the dew point, that moisture will eventually condense on the surfaces of the internal parts of the system. Meanwhile, condensation on car AC vents has several effects on the system.

Leaks in the AC System

Leaks in the air conditioning system usually occur due to poor installation or damaged hoses and seals. If leaks occur in the AC, moisture will be allowed to enter the system, resulting in higher humidity levels within the car.

Blocked Air Filters

Clogged air filters can also lead to moisture in the AC system. The components are designed to last for a specific time frame.

However, they may become blocked with dirt or debris over time due to constant use. This can further freeze the system’s evaporator coils, resulting in excess water leaks.

Compressor failure

A failed compressor is another reason you may experience moisture in your air conditioning system. A malfunctioning compressor can trigger refrigerant leaks, leading to moisture build-up and condensation in the AC.

Besides moisture, this situation can introduce bacteria, mildew, and mold into the air conditioning system.

Symptoms of Moisture in Car AC System

Virtually every vehicle malfunction or problem is accompanied by obvious symptoms that serve as a signal. Moisture in the car’s air conditioning system is no exception.  The following are some common symptoms of moisture in AC system.

Nasty odor

When mold, bacteria, or mildew gets into your car’s AC due to moisture in the system, their presence will eventually produce a nasty odor. This usually occurs when you fail to remove the moisture immidiately.

Who likes to drive in a car with an offensive odor? Of course, that’s embarrassing to experience, especially when you’re not alone in the car. Hence, you shouldn’t overlook this situation.

High humidity/foggy windows

Moisture will also cause your car’s window to fog up when you start the engine and turn on the air conditioning system. You can also experience high humidity when water leaks from your AC and vaporizes into the cabin.

Poor cooling or airflow

Poor cooling or airflow is another sign that you most likely have moisture in your air conditioning system. This is usually a result of condensation or water collecting in the ducts, thereby blocking the airflow.

Frozen evaporator coil

Lastly, too much moisture can also cause the air conditioning system’s evaporator coil to freeze. This will usually happen due to condensation in your AC system caused by the coil freezing up and resisting airflow.

How to Prevent Moisture Formation inside Your Car AC

There are several ways to avoid moisture formation or condensation from car AC. Implementing these prevention strategies is easier and cheaper than fixing a faulty AC system.

The following tips will help prevent moisture from forming in your car’s air conditioning system.

  • Clean up your AC fan and air vents regularly.
  • Inspect for leaks in the AC system and fix them as soon as possible.
  • Clean up dust from the AC Condenser regularly, and use specifically recommended cleaner.
  • Service the air conditioning system regularly.
  • Turn off the AC fan and open your car’s windows when you park in hot weather.
  • Replace the air filter in your air conditioning system regularly (once a year at least).

In most cases, these prevention strategies require consistency. In other words, cleaning the fan, air vents, or other AC areas should be done once and again as long as you desire to prevent moisture formation and other AC faults from occurring in your car.


Moisture breeds several adverse effects in your car if not checked on time. The offensive odor that comes from bacteria or mold in the AC system due to moisture can be frustrating.

That’s why understanding how to remove moisture from car AC system is important. However, you must first take out time to verify and ascertain the exact cause of the moisture in the air conditioning system.

Afterwards, implement a fix-up strategy that aligns with the diagnosed problem. If you’re unsure of handling the process of removing moisture from your car’s AC, do not hesitate to contact an expert auto technician to handle the job.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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