Why does water drip from under the car when the air conditioning is on?
2 Answers
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. The moisture in the hot air inside the car condenses on the heat-absorbing fins of the evaporator, and the water droplets are collected by the plastic housing of the evaporator and drained out of the car through a pipe. The functions of the air conditioning system are as follows: 1. The air conditioner can control the temperature inside the cabin, heating or cooling the air to maintain a comfortable level; 2. The air conditioner can remove moisture from the air. Dry air absorbs sweat from the body, creating a more comfortable environment; 3. The air conditioner can intake fresh air, providing ventilation; 4. The air conditioner can filter the air, removing dust and pollen.
That day, I had the car air conditioning on, and there was a constant dripping sound of water underneath. I thought something was wrong and nervously rushed to the repair shop to ask. The mechanic laughed and said it's perfectly normal—the air conditioning works like a refrigerator; when cooling, it absorbs the hot air inside the car, and the moisture turns into water droplets that gather on the evaporator and drain out through a tube. In summer, when humidity is high, the water is more noticeable, especially after being stuck in traffic or driving on the highway. If water leaks into the car and the carpet gets wet, that’s when there’s a real problem—it might be due to leaves or debris clogging the drain pipe, which needs to be cleared immediately to prevent mold and odors. I’ve been driving for ten years, and I remember one time I forgot to check, almost damaging the wiring. Since then, I’ve made sure to clean the drain outlets during regular maintenance—don’t make a big deal out of it, but saving money is important.
