Why Does My Car Leak Water When The Ac Is On?

If you’ve ever noticed water dripping from under your car while the air conditioning (AC) is on, you may be wondering what’s causing it. It’s normal for water to form and collect underneath the car, but excessive water or a constant drip can indicate a problem. This article will explain why your car may be leaking water when the AC is on.

Condensation from the AC System

The most common reason for water to leak from your car when the AC is on is due to condensation. The AC system works by removing heat and humidity from the air inside the car. As the warm and humid air passes over the evaporator coils in the AC system, moisture condenses on the coils and drips down into a drain pan located underneath the coils.

The drain pan has a small drain hole that allows the water to flow out of the pan and onto the ground. Over time, this drain hole can become clogged with debris, such as dirt, leaves, and insects, which can cause water to back up and overflow onto the floor of the car.

Additionally, if the AC system is not used frequently or is only used for short periods of time, the evaporator coils may not get cold enough to cause condensation to form, which can result in a lack of water drainage.

Damaged or Clogged Drain Tubes

Another reason for water leakage could be due to damaged or clogged drain tubes. The drain tubes are responsible for channeling water from the drain pan to the ground. If the tubes are damaged or clogged, water will not be able to flow out of the pan, causing it to overflow and leak into the car.

To check for damaged or clogged drain tubes, you will need to locate them under the car. They are typically located near the front passenger side of the vehicle, but the location may vary depending on the make and model of the car. Check for any visible signs of damage or debris, and if necessary, use a wire or compressed air to clear any clogs.

Malfunctioning AC System

In some cases, water leakage could be a symptom of a malfunctioning AC system. For example, if the evaporator coils are dirty or damaged, they may not be able to cool the air passing over them properly, which can result in excessive condensation and water leakage.

Other potential causes of a malfunctioning AC system include a low refrigerant level, a faulty compressor, or a blocked expansion valve. If you suspect that your AC system may be malfunctioning, it’s best to take your car to a qualified mechanic for diagnosis and repair.


Water leakage from a car when the AC is on is a common issue that is usually caused by condensation from the AC system. However, damaged or clogged drain tubes or a malfunctioning AC system can also be the culprit. Regular maintenance and inspection of your AC system can help prevent water leakage and ensure that your car stays in good condition. If you notice any excessive water or dripping, it’s important to address the issue promptly to avoid damage to your car’s interior.

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