Is Excessive Drainage from Car Air Conditioning Normal?

[KathrynLynn]

Excessive drainage from car air conditioning is a normal phenomenon. The reason for the drainage is: the car cooling system is equipped with an evaporator inside the dashboard. When the air conditioning is turned on, the surface temperature of the evaporator is relatively low, causing the moisture in the hot air inside the car to condense on the heat-absorbing fins of the evaporator. The water droplets are then collected by the plastic casing of the evaporator and drained out of the car through a pipe. Car air conditioning, also known as the car air regulation device, serves the following purposes: 1. Adjusting and controlling the temperature, humidity, air cleanliness, and air flow inside the car to an optimal state; 2. Providing a comfortable environment for passengers and reducing travel fatigue.

[DiAva]

Last time I drove my family to the seaside for vacation, I was startled to find water gushing under the car when the air conditioning was on at noon. I specifically went to the 4S store to ask, and the mechanic said this is a completely normal phenomenon of air conditioning condensate. Especially in humid southern weather or when the air conditioning is used for a long time, it's normal for the drain pipe to drip a puddle of water. The principle is actually like water droplets forming on the surface of a chilled beverage bottle; the car's air conditioning cools the evaporator, which also condenses moisture from the air. The key is to check if the drainage position is correct—normally, it should drain from the chassis to the ground, and the water should be clean. If you find the driver's seat footwell wet or the water has a musty smell, it might indicate a clogged drain pipe that needs attention. Otherwise, there's generally no need to worry.

[BrookeLynn]

I've been driving for over a decade and many friends have asked about this issue. When parked in an open-air parking lot for several hours in summer, there's often a patch of water under the chassis - nine times out of ten it's from the AC drainage. When the air conditioning cooling system operates, it condenses the humid air inside the car into water, which is then drained outside through a dedicated drainage pipe. The higher the humidity or the lower the AC temperature setting, the greater the amount of water drained - this actually indicates good cooling performance. I remember once during a long drive in heavy rain with recirculation mode and cooling on, the drainage after two hours was so much it wet the tires. As long as the water isn't leaking from the ceiling or seats inside the car, there's no need to worry.

[StLouis]

Last week during maintenance, I asked the technician, and he demonstrated with a water glass: pouring ice water into a hot glass causes condensation to instantly form on the walls. The car's air conditioning works on the same principle—the lower the evaporator temperature, the greater the condensation output. The more humid and hot the weather, the more water drains outside the car, sometimes even resembling a small waterfall. If the liquid leaking under the chassis is clear and odorless, it's just normal AC drainage. However, if the water is murky or leaking into the cabin, the drain tube might be clogged with mud or leaves. It's best to clear it promptly, as debris can easily block the drainage holes in the chassis.

[VonElaina]

Both of our family cars have this issue, especially during the rainy season when water pools under the car after parking with the AC on. At first, I thought it was a malfunction, but the mechanic explained that it's the AC expelling moisture, just like how a home AC unit drips water externally. The higher the temperature and humidity, or the longer the AC runs, the more water is expelled. However, there are three things to note: first, check if the drainage is under the chassis; second, smell the water for any musty odor; third, inspect if the car interior is damp. As long as the drainage is normal, a large amount of water actually indicates good dehumidification performance of the AC, so there's no need to worry at all.