AC Water Leak: Car Air Conditioning and Its Problems

If you are facing the challenge of AC water leak, car that you are using has faulty air conditioning, which definitely requires a service.

Car Leaking Water From Air Conditioning

The causes of this issue are the wrong installation of the HVAC component, drain/pan problems, and damaged components. Our car experts will discuss how to fix the issue in this article.

What Causes Water to Leak From a Car Air Conditioner?

Drain (or drip) pan problems, incorrect installation of the HVAC system components, issues with the refrigerant and evaporator, and damaged components like seals can cause water to leak from a car air conditioning system. Other causes are the improper attachment of the drip pipe and blocked windshield cowl drain.

– Condensate Drain Pipe Blockage

A blocked condensate drain (also called an AC drain) can cause water to leak into your car. For your AC to cool your car’s interior, it needs to extract moisture from the air entering your car. After the cooling is done, this moisture is condensed back to water and drained out via the AC drain in your car.

Causes for Car Leaking Water From Air Conditioning

Over time, this drain can get blocked by dust and dirt particles, preventing the condensed water from draining out of your car.As a result, you will find water overflowing inside the car. Your car’s drain line can easily get blocked because sections of it are exposed to sand and dirt on the underside of the vehicle.

– Improperly Attached AC Drain

When the AC drain is not well attached to your car’s ventilation system, water won’t drain out properly, so you’ll find leaks inside your car. Sometimes, the issue might not be in the installation but in the size of the drain installed. If the AC drain is too small, you may get leaks.

– Dirty/Blocked Air Filters

An air/AC filter that is dirty or blocked can also cause your AC to leak in your car. The role of the AC filter is to block dust, dirt, and debris from entering your car’s HVAC internal components.


Over time, your car’s AC filter will accumulate dirt and dust. The filter will get blocked completely if you do not remove these particles. When a car’s AC filters get blocked, they freeze up its evaporator coils. In turn, this freezing will cause water to overflow from the condensate pan and leak into your car’s interior.

– Damaged Condensate Drain Pan

A damaged or broken condensate pan can also make your AC leak water into your car. This pan collects condensate water after the air conditioning unit has finished cooling your car.

Over time, this pan suffers wear and tear and corrosion. If the pan breaks or gets damaged, it won’t be able to hold water as it should, so you’ll get water leaks inside your car.

– Blocked Windshield Cowl Drain

A blocked windshield cowl drain is another common cause of leaking air conditioning units. Cowls protect the windshield wipers and cabin filters from dirt. It is always found at the bottom of the windshield and often covered by a sheet of plastic or metal that connects to the car’s drain channels. The water in the windshield cowl is designed to exit through the drain plugs of a car.

As you continue to use your car, debris, dust, and leaves can block the cowl slots and seep into the air filter or drip pipes, causing clogging. This clogging will later result in leaks. Meanwhile, extreme weather conditions/elements can also cause rust formation in the cowling seals, creating an avenue for water leaks.

– Evaporator Issues

Evaporator problems can also cause leakage of AC water in your vehicle. The role of an evaporator is to release cool air into the cabin. This car part is usually blocked, causing excessive water that should’ve drained outside the car to go back up into the evaporator core. If this continues, the evaporator will get flooded, and some of this excess water will go into the AC vents.

If you notice water dripping out of the AC vents in your car, it’s a serious sign that your AC evaporator is flooded. Other times, you may notice a strange smell whenever you put on the AC.

– Wrong Installation of HVAC Components

Improper installation of the HVAC components in your car can also cause leaky air conditioning units. Sometimes, errors can occur during servicing or DIY fixing of AC components. Any improperly installed component can affect the performance of the entire AC unit and cause leaks.

– Contaminated or Low Refrigerant

Low refrigerant levels can also make your air conditioners leak. To circulate cool air in the cabin, your vehicle’s AC needs a certain amount of refrigerant. This refrigerant works with the expansion valve to cool your car.

When the amount/level of refrigerant reduces, the AC pressure also decreases. If the refrigerant isn’t refilled, the evaporator’s coils will freeze and cause the drain pans to overflow and leak into the car. Also, when your car’s refrigerant level is low, your car will occasionally release hot air.

– Outdoor Temperatures

Outdoor temperatures can weary your AC unit and cause leakages. In very hot climates, your AC will absorb more moisture from the air. In cold climates, the evaporator coils will freeze. In both cases, you’ll find that your AC will leak, even when there’s nothing wrong with any of the components.

– Condensation of the AC System

Condensation is necessary for any AC system to work. Most times, when you notice that water is dripping from the underside of your car after parking, your AC is the culprit.

As your AC draws in fresh air (which contains more moisture) for cooling and distribution, it must condense this air and release the corresponding amount of water through the drain. If you wish to minimize the condensation, you should use the recirculation setting on your AC rather than the fresh air setting.

– Damaged Components

If one or two components of your car’s AC system are damaged, water leaks into your vehicle when you use your AC. Sometimes when your vehicle’s AC leaks water, it isn’t because you have blocked filters or drains but because one or more critical components of your HVAC system have gotten damaged.

A car’s AC system is sensitive. All its components must be in perfect shape; otherwise, issues like unregulated air and unwanted leaks may occur.

– Failed Seals

Failed/broken seals can also cause your car’s AC to leak. Every car’s AC system uses rubber seals, making the whole system leakproof. If one or more of these seals break or fail, water will leak through them into your car.

Seals wear out with time, so it is advisable to go for AC system checkups and repairs regularly (at least once a year) so damaged seals can be replaced.

How To Fix Car Air Conditioner Leaking Water

To fix an AC that’s dripping water, you can inspect and clean the windshield cowls (and do so regularly), check if the AC drip pipe is well attached (and attach it if it’s not), unblock the condensate drain hose, and see a mechanic for proper repair.

– Inspect and Clean Cowls

Carrying out routine checks on your car cowl is very important. Check for holes, debris, and early signs of corrosion. If you find any rust, use a wire brush to remove it. Apply a rust concealer to stop the rust from spreading to other areas of your car.

If your cowls are clogged, remove the larger obstacles first, such as leaves and small sticks. Then use an air compressor to blow away all the smaller debris you find. This saves you the risk of ending up with a blocked drip pipe. You can also use a high-pressure hose to clear the cowl.

– Check if the AC Drain Is Properly Attached

To do this, you need to locate the drain first of all. It’s usually found under the evaporator and is always at the lowest part of the HVAC system. If you’re having trouble finding the AC drain, try finding the evaporator first (which is always located inside the passenger compartment) or consult your vehicle manufacturer’s manual.

– Unblock the Condensate Drain Hose

You need to find the drain hose to unblock the AC drain. Most times, it’s located on the far back side of the engine, on the passenger side. Once you’ve found it, remove the cap and try to bend or squeeze the hose to release the debris inside. You can also use a slender metal like a screwdriver to force out anything causing a blockage in the hose.

Solutions for Car Leaking Water From Air Conditioning

If it doesn’t seem OK after that, use a cleaning solution (never use bleach) to dissolve the blockage, then push it out with your screwdriver. Finally, flush out the hose with water and replace the cap.

– See a Mechanic

A car’s AC system can be sensitive and complex. Trying to repair delicate components may end up causing further damage if you don’t know what you’re doing. This is why it is advised that you limit your DIY fixes to things like flushing drain pipes and cowls. If the problem is other delicate components in the AC system, you should see a mechanic for proper air conditioning repair.

Conclusion of Car Leaking Water From Air Conditioning

Can an AC water leak be a cause of a car overheating when the AC is on and idling?

Yes, an AC water leak can contribute to a car overheating with the AC on. When the AC is running, it produces condensation that is usually drained away. However, if there’s a leak in the AC system, the water can escape onto important components, like the radiator. This can hinder proper cooling and result in car overheating with AC on, particularly when idling.


Now you know what causes water to leak from a car AC,

here’s a summary of the basic things you should do when you find your car leaking water from the AC:

  • Check for blocked drains, cowls, and damaged pans if water leaks from your car AC.
  • Unblock drains and cowls with necessary tools like an air compressor, a screwdriver, or a high-pressure water hose.
  • Check for any improperly installed components of the HVAC system.

Remember that prevention is better than cure. Routine checks and repairs to your car’s AC system can save you the trouble of having leaks in your car in the future.

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