What Causes Excessive Water in the Car's Air Conditioning Filter?
3 Answers
If water drips outside the car (under the vehicle) onto the ground, this is a normal phenomenon, generally caused by the following reasons: 1. The plastic casing of the evaporator collects water droplets: Because the car's air conditioning system is equipped with an evaporator inside the dashboard, when the air conditioning is turned on (A/C button ON), the surface temperature of the evaporator becomes very low. Moisture from the hot air inside the car condenses on the heat-absorbing fins of the evaporator and is collected by the plastic casing of the evaporator, then drained out of the car through pipes. If the vehicle is parked for a while, you may sometimes see a puddle of very clean and transparent water, which is no cause for concern about vehicle malfunction, as the engine's coolant is usually antifreeze (green, red, or blue). 2. Condensation of moisture from the air on the surface of the pipes: If the low-pressure pipes are not wrapped with insulation foam, the surface of the pipes can easily condense moisture from the air, and water droplets often gather and drip from the lowest point of the pipes.
Having driven my own car for over a decade, I believe the most common cause of water accumulation in the cabin air filter is a clogged drainage system. When the air conditioning cools, it condenses moisture which should normally drain out of the vehicle through the drain tube. However, if the drain outlet gets blocked by dust or leaves, the water flows back into the filter area. Another possibility is improper installation or aging/cracking of the filter itself, allowing water to seep in. This is especially prone to happen during rainy seasons or after car washes when humidity is high, making moisture buildup more likely. My car had a similar issue before – whenever the drain tube got clogged, the filter would become soaking wet. If not repaired promptly, the system can develop mold and odors that affect health. I quickly used a thin stick to clear the drain outlet to prevent recurrence.
I noticed water droplets in the air conditioning filter shortly after buying the car, which really worried me. It might be due to leaves blocking the drain pipe when parked, causing water to accumulate in the filter, or excessive condensation inside the AC system. Last time I asked a friend, he said high humidity, like during the summer rainy season, can also cause this, and if the filter is misaligned, it might even leak. I don’t know much about car repairs, so I had to take it to a repair shop. Water lingering inside isn’t just uncomfortable—it makes the interior damp, prone to bacteria, and affects both breathing and driving mood.
