Why does the car drip a lot of water when the air conditioner is on?
4 Answers
Condensation from the air conditioner. Reasons why the car drips water when the air conditioner is on: 1. Condensation of hot air on surfaces: Because the car's air conditioning system has an evaporator installed on the dashboard, when the air conditioner is turned on (the air conditioning key is turned on), the surface temperature of the evaporator is very low. The moisture in the hot air inside the car will condense on the heat-absorbing fins of the evaporator, and the water droplets are collected by the plastic housing of the evaporator and discharged out of the car through a pipe. 2. Condensation of air: Outside the compressor (low-pressure area) in the engine compartment, the moisture in the condensed air will also fall to the ground (sometimes the amount of water is greater than the drainage from the evaporator). 3. Lack of insulation foam covering: If the low-pressure pipe is not covered with insulation foam, moisture in the air can easily condense on the surface of the pipe, and water droplets usually accumulate at the lowest point of the pipe.
Yesterday, I encountered this exact issue while repairing a car. The owner's AC drain pipe was completely clogged. When the AC cools, condensation forms on the evaporator, just like water droplets on a chilled soda can. Normally, the water drains out through a small rubber tube under the chassis. But if the tube gets blocked by mud or leaves, the water has nowhere to go but back into the cabin. The worst case I've seen was passenger footwells so flooded you could raise fish in them! So never ignore water pooling under your car. My advice: check and clear the chassis drain ports with an air gun before summer each year—way cheaper than replacing soggy carpets.
Air conditioner dripping is very common. My old car now leaks like a water curtain cave when the AC is on. It's actually condensation forming when warm air hits the cold evaporator, just like fogging on windows in winter. But pay attention to the amount and location of water - normal dripping should be directly under the car. If the floor mats get wet, there's an 80% chance the drain tube came loose. Last week my buddy's passenger side got flooded because a rat chewed through the drain pipe. Easy to check yourself: after turning off the engine, look under the car for that thin plastic tube and clear it with a wire. By the way, a dirty cabin air filter can also increase condensation - don't skimp on this small expense.
Last week when dropping off my child at school, I noticed there was always a puddle of water under the parking spot, so I specifically went to the repair shop for consultation. The technician said that more condensation water is a sign of powerful air conditioning performance, but excessive amounts might indicate overcharged refrigerant causing the evaporator to become too cold. Some cars have design flaws such as insufficient slope in the drainage pipe, or the drainage pipe being flattened during floor mat modifications. They used an endoscope to inspect under my car and suggested it's best to check if the drainage outlets are clogged with mud before each rainy season. Additionally, don't turn off the air conditioning immediately after parking; running the natural air for two minutes can dry out the pipes to prevent mold.
