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What Does Water on Your Car's Floor Mean for Your AC System?

26 July 2023 by Herman Mills

Water suddenly appearing on your car's floor can be a frightening experience. Has your car sprung a leak? Are your door seals failing? While issues with the water channels around your door or other weatherproofing areas may be to blame, these problems often produce water at the base of the window or floor.

Surprisingly, water on the floor underneath your dash often indicates an issue with your car's AC system. Keep reading to learn three reasons why an air conditioning system problem can lead to soggy feet and what you can do to repair the issue.

1. Your Condensate Drain Might Be Clogged

Have you ever noticed water pooling beneath your car on a hot and humid day? Your air conditioning system has the happy side effect of dehumidifying the air as it moves heat inside your cabin to the outside world. The water removed from the air should normally drip through a small drain line or tube underneath your car.

If this drain tube becomes clogged, water will back up at your car's drain pan. This pan is directly underneath the evaporator coil, inside your cabin behind the dash. Enough water flowing back into the pan can spill over and create a damp carpet. You can try cleaning this drain tube yourself, but a severely clogged drain line may require replacement.

2. You Might Be Losing Refrigerant

Another possibility is that a large volume of water is overwhelming your car's condensate drain line. Even on humid days, normal system operation should not produce enough water to overflow a clean, undamaged condensate drain. However, low refrigerant levels can cause large amounts of ice to form on the evaporator coil.

The ice will eventually completely insulate the evaporator coil, preventing it from transferring additional heat to the remaining refrigerant. This condition usually results in short cycling, and the thawing ice can produce large amounts of water when the system shuts down. If you suspect a refrigerant leak, you'll need a qualified repair shop to investigate the problem and locate the source.

3. You Have an Airflow Issue

Airflow problems can lead to symptoms that initially look like refrigerant leaks. Your evaporator coil relies on constant warm air to transfer heat through the system. Insufficient airflow will make the evaporator coil very cold, creating an icy insulation layer like a refrigerant leak. The thawing ice can flood the cabin floor when the system inevitably shuts down to protect itself.

Your cabin filter is the easiest component to check if you suspect an airflow restriction. An old or clogged filter can restrict airflow enough to freeze your evaporator coil. If replacing the filter doesn't work, you'll need an experienced AC repair shop to investigate the system for possibly blower motor issues that may be reducing overall airflow. Find a certified mechanic near you if you require car AC system repairs.

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