Though summer driving is significantly different from traveling throughout the rest of the year, the biggest difference is that you will likely make use of your air conditioning a lot more often. When you notice a leak from beneath your vehicle, your immediate reaction may be to panic and begin to look for the source of the drip. But if you see the leak after the air conditioner has been running, it may be completely normal. Water dripping underneath a vehicle is actually a fairly common occurrence when running your air conditioning, especially when it's hot or humid outside. The water pooling under your vehicle is condensation draining from the evaporator's drain tube due to the normal function and design of the A/C evaporator. In this article, we’ll describe what causes water to leak from under your vehicle in the summer so you can better understand this occurrence.
The A/C Evaporator Produces Condensation
Air conditioning evaporators are heat exchangers, just like a radiator or heater core, but for the A/C system. They allow cold, low-pressure liquid refrigerant to absorb heat from the evaporator case (the box all of your heating and A/C components are stored in), converting the refrigerant's state into high-temperature gas before it's sent to the compressor to be re-pressurized. In clutch-cycling orifice tube (CCOT) systems, the refrigerant leaving the evaporator is more vapor than gas, and is collected in an accumulator to give it time to reach the appropriate temperature and state while also filtering it before the refrigerant moves to the compressor. This process of refrigerant conversion in the evaporator and the rapid cooling of the evaporator case can produce condensation. For this reason, a drain tube is installed on the bottom part of the case, and passes through the passenger floorboard to give the condensation a place to exit the A/C system and the car.
A/C Refrigerant Leaks
The thing about refrigerant is that it rarely leaks as a liquid, and if there is a leak in your A/C system, the refrigerant is often escaping as a vapor because refrigerant continuously changes state. For refrigerant to leak as a liquid, the A/C system would have to develop a leak in parts of the system where the refrigerant is still in a liquid state, and the damage caused would have to be significant or large enough to form drips. It can happen, but in most cases, small gaps in fittings or seals are enough to allow refrigerant vapor to escape. This usually happens well before a dripping leak develops, making it very unlikely that the puddle under your vehicle is the result of a refrigerant leak.
Flooded Floorboards Caused by Clogged A/C Condensation Drain Lines
If your car is leaking water on the passenger side cabin floorboard, you may have a clogged evaporator drain tube. This is not uncommon, and often simply requires the tube to be cleaned out and any clogs or debris removed to allow the condensation to flow freely out of the case. In some cases, you may instead notice coolant on your passenger floor, which indicates a damaged and leaking heater core (and maybe a clogged drain tube as well). Determining what type of fluid is on the floorboard of your vehicle should be the first step in diagnosing and repairing the problem. If the evaporator drain tube is clogged, the repair may be as simple as clearing the tube, but if it’s deteriorating or otherwise damaged, or if the heater core is leaking, more intensive repairs should be completed and the drain tube may need to be replaced to allow condensation to drain.
What is Leaking from My Car?
Hopefully this has helped you better understand why you may see water under your vehicle when using your A/C. If your A/C system is not working correctly, you can find all the parts and A/C chemicals you need for your repair at O’Reilly Auto Parts. We can also help you better understand how to recharge your A/C and why your air conditioner isn't working with resources in our How-To Hub. If you're not comfortable performing A/C repairs or service yourself, check out our Find a Repair Shop tool to find a trusted shop near you, or stop by your local store and one of our parts professionals will be happy to recommend a shop for your repair.