Why does water drip from the chassis when the car's air conditioner is on?

[KatherineDella]

It is normal for water to leak from under the chassis when the car's air conditioner is turned on. The dripping water under the car is usually condensation from the air conditioner, and it is normal for it to drip below the passenger seat. The air conditioner's compressor compresses the refrigerant, which then expands through a valve, releasing heat and lowering the temperature of the refrigerant. Since there is a lot of water vapor in the air, when it encounters the very cold evaporator, it turns into water. If there is a lot of condensation, it will flow out of the air conditioner's drain. Below is an introduction to air conditioner maintenance: 1. Comprehensive inspection of the air conditioner: When using the air conditioner for the first time in summer, check the air conditioning system, such as inspecting the refrigerant through the reservoir, whether the air filter is too dirty, and whether there are foreign objects in the radiator. 2. Pay attention to cleaning the air conditioner: The air filter should be replaced regularly; otherwise, the air conditioner may produce a musty smell. Additionally, the condenser should be cleaned periodically, and the radiator should be removed for thorough cleaning.

[AidenDella]

As a car mechanic who has driven many vehicles, it's normal to see water dripping from the undercarriage when the air conditioning is on. That's the condensation from the AC system. When cooling, the hot air inside the car condenses on the evaporator, forming water droplets that drain through a small tube underneath the car, usually near the front on the driver's side. This is more noticeable in hot, humid weather, similar to condensation on a cold glass in summer. Clear, odorless water dripping in moderate amounts is a good sign, indicating effective dehumidification by the AC. However, if there's excessive water flow, persistent dripping, unusual odors, or abnormal colors like blue or green (which could indicate coolant leakage), it may affect the AC system or airflow and requires prompt inspection to avoid major repairs. Normally, a small puddle under the car when parked is fine, but continuous flow isn't typical. Keep the drain hole clear.

[JayceFitz]

As an ordinary office worker, I've been commuting by car for several years. Every summer when I turn on the air conditioning and park, I always notice water dripping from the undercarriage. At first, I thought it was an oil leak and got quite startled, but later learned it's just normal condensation water discharge from the AC system. This process involves water droplets condensing as the air cools, then dripping out through the drainage tube, forming a small puddle of clear, odorless water under the front of the car. It's more noticeable during hot weather or rainy seasons when using AC, and stopping after a while is normal. From my personal experience, if there's no water at all, I'd actually worry about poor dehumidification function of the AC. Occasionally, if there's excessive water, it might indicate clogged pipes needing cleaning. I routinely observe and gently tap the undercarriage inspection holes when parking to prevent dust accumulation that could cause odors.

[VanLondon]

I prioritize driving safety. Water dripping from the chassis when the air conditioning is on is generally normal condensation—moisture removed during air cooling exits through small holes in the undercarriage. However, be alert for abnormalities: if the dripping water has an unusual odor, abnormal color (e.g., red), or excessive/unstoppable flow, it may indicate coolant or AC system leakage, leading to internal water accumulation, mold growth, and even compromised airflow or driving safety. Normal dripping occurs near the front chassis—clear and intermittent. After parking, briefly check the water quality; address abnormalities early to prevent risks.