How to clean evaporator drain tubes

The air conditioning system in a car has evaporator drain tubes that need to be cleaned if the car has dirty air or uneven airflow.

Modern air conditioning systems are made up of several individual components that convert the warm air in the cabin into cool and refreshing air. However, there are times when the air blowing into the cabin is not as refreshing or cool as one would like. While there are several reasons that lead to poor performance of an air conditioner, one of the most commonly overlooked is problems with clogged or dirty evaporator coils or obstructions inside the evaporator drain tube.

When water is contained within any object, the introduction of heat and oxygen allows the microscopic organisms living in our water to become an ideal environment for mold and harmful bacteria to grow. These bacteria attach to internal metal parts inside the evaporator and can restrict the flow of refrigerant and liquids inside the unit. When this happens, bits of bacteria or debris are shed off the coils and can get caught in the evaporator drain tube, as it has a 90 degree bend in most cases. If this happens to you, you need to clean the evaporator drain tube as well as the evaporator itself.

The A/C drain hose, or evaporator drain hose as it is often called, is located on the side of the engine bay of the firewall. On most domestic and foreign vehicles, the air conditioning evaporator is located inside the cabin, directly between the firewall and the bottom of the dashboard. Most car owners and amateur mechanics choose to clean the A/C drain hose when symptoms appear (which we will cover in the next section below) rather than removing the evaporator housing and completing a heavy evaporator cleaning.

ASE certified mechanics as well as vehicle manufacturers recommend cleaning the evaporator body from the vehicle and cleaning this assembly at the same time as cleaning the evaporator drain hose. The reason you want to take this extra step is because the debris causing the A/C drain hose to malfunction is inside the evaporator body. If you just clean the tube, the problem will return sooner than you think, and the process will have to be repeated again.

We will show you the steps you must follow to clean the evaporator body and clean the internal components of this critical air conditioning system, as well as to remove debris from the evaporator drain hose.

Part 1 of 2: Finding Signs of Evaporator Drain Tube Contamination

Dirty evaporators have several signs that indicate that they are dirty and need to be cleaned. The evaporator is designed to convert warm and often humid air into dry and cooler air. This process removes heat and humidity using a refrigerant circulating through a series of metal coils. When this happens, the moisture turns to liquid (H2O) and must be removed from the evaporator to reduce mold and mildew. Below are a few common warning signs that there is a problem with the air conditioner evaporator and that it needs to be cleaned.

Stale or dirty air coming from air conditioner vents: When bacteria, mold and mildew gather inside the evaporator, the residue seeps into the air it tries to cool. Once this cold air is circulated through the vents, it becomes contaminated with bacteria, which often causes musty or musty smells in the cabin. For most, this musty and dirty air is rather annoying; however, for those people who live with chronic obstructive pulmonary disease, or COPD, which is 25 million people in the United States, according to the CDC, bacteria in the air can cause irritation or exacerbation of COPD, which often prompts hospital visits.

The air conditioning system does not blow constantly: Another common symptom that alerts a vehicle owner to an evaporator problem is that the air entering the cabin is intermittent and uneven. The AC system has a control system that allows the fans to run at a set speed. When the inside of the evaporator becomes clogged with debris, it causes an inconsistent air flow to the vents.

There is an unpleasant smell in the car interior: Since the evaporator is located between the dashboard and the firewall, it can emit an unpleasant odor if it is clogged with excess bacteria and debris. It eventually ends up in the interior of the car, creating a very unpleasant musty smell.

When bacteria and debris form inside the evaporator, they break off and drain into the evaporator tube. Since the tube is usually made of rubber and usually has a 90 degree elbow, debris blocks the inside of the tube, which reduces the flow of condensate from the evaporator. If not repaired, the evaporator will fail, which can lead to costly replacement or repair. To reduce this possibility, cleaning the evaporator and clearing the blockage in the tube with the steps we outline below is usually the best course of action.

Part 2 of 2: Cleaning the Evaporator Drain Tube

On most domestic and imported cars, trucks and SUVs, the AC system works in a similar pattern to the one above. The evaporator is usually located on the passenger side of the car and is installed between the dashboard and the firewall. You don't need to remove it to clean it. In fact, there are several OEM and aftermarket AC evaporator cleaner kits that include one or two different aerosol cleaners sprayed into the evaporator when attached to the evaporator tube.

Necessary materials

• 1 can of evaporator air conditioner cleaner or evaporator cleaner kit
• Pallet
• Replacing the Cabin Filter(s)
• Safety glasses
• Protective gloves

To accomplish this task, you need to make sure you have easy access to the evaporator drain tube. On most cars, trucks and SUVs this tube will be located in the center of the vehicle and in many cases near the catalytic converter. Make sure you prepare the vehicle for service by raising it on a hydraulic lift or by jacking up the vehicle as outlined in the sections above. You won't have to disconnect the battery cables as you won't be working with anything electrical during this cleaning.

Step 1: Raise the car. Make sure you have easy access to the vehicle's chassis.

The problem with using jack stands is that sometimes fluid gets trapped inside the evaporator and doesn't drain completely out of the car when it's raised. To avoid this, raise the entire vehicle on four jacks.

Step 2: Get under the bottom and find the evaporator drain tube.. Once the car is raised enough for you to have easy access, locate the evaporator drain tube.

On many cars, trucks, and SUVs, it is located very close to the catalytic converter. Once you've found the tube, place a drain pan right underneath it and make sure you have a can of evaporator cleaner for the next step in this process.

Step 3: Attach the nozzle of the cleaner bottle to the bottom of the tube.. The purifier jar usually comes with an extra nozzle and a spray wand that fits into the evaporator tube.

To complete this step, follow the evaporator cleaner manufacturer's instructions. However, as a general rule, you should remove the top of the can, attach the nozzle tip to the evaporator drain tube, and pull the trigger on the can.

As soon as you attach the spray nozzle to the can, in most cases the can will automatically begin to deliver foam cleaner to the vaporizer. If it doesn't, go to the next step.

Step 4: Pour ½ of the contents of the jar into the evaporator.. In most cases, the cleaning agent from the can is automatically dispensed into the evaporator.

If it doesn't, simply press the spray nozzle on the top of the can to inject the cleaning foam into the vaporizer. The instructions for most products recommend spraying ½ of the contents of the can into the evaporator, allowing the foam to soak in for 5-10 minutes.

Do not remove the nozzle from the evaporator drain tube, otherwise the contents will spill out prematurely. Wait at least 5 minutes before picking up the handset.

Step 5: Remove the nozzle and let the contents drain. After the foam cleaner has been absorbed for at least 5 minutes, remove the nozzle fitting from the evaporator drain tube.

After that, the liquid will begin to quickly flow out of the evaporator. Allow the contents inside to drain completely from the evaporator.

• Attention: While the evaporator cleaner is draining, you can save time by preparing the next step of the cleaning process. You will need to remove the cabin air filter from inside the car. Many mechanics let the liquid drain until it slowly drips. Leave the pallet under the vehicle, but lower the vehicle with a jack or hydraulic lift. This speeds up the liquid flow inside the evaporator.

Step 6: Remove the Cabin Filter. Since you are cleaning the evaporator and the evaporator drain tube, you will also need to remove and replace the cabin filter.

Follow the instructions for this step in the service manual as they are unique to each vehicle. If you are going to use the cabin filter cleaner included with most evaporator cleaning kits, remove the filter and insert the cartridge before following the steps below. You don't want to have a new or old filter in your cabin cartridge because you're spraying cleaner into the air vents.

Step 7: Clean the air conditioner vents. Most vaporizer cleaning kits include an aerosol can to clean the inside of the vents.

This improves the smell inside the car and removes potentially harmful bacteria trapped in the air vents. The general steps for this are: first, remove the cabin filter and start the engine.

Turn off the air conditioner, open the vents to outside air, and turn the vents on to maximum power. Close the windows and spray the entire contents of the aerosol cleaner into the vents under the windshield.

Turn off the ventilation and muffle the car.

Step 8: Keep windows closed for 5 minutes.. Then you roll down the windows and let the car air out for 30 minutes.

Step 9: Remove the pan from underneath the vehicle..

Step 10: Lower the car.

Step 11: Clean the inner coils. After completing this process, the evaporator drain hose should be disconnected and the internal evaporator coils cleaned.

The cleaners are designed to keep cleaning the coils for a while until the condensation naturally pushes them out of the car. Occasionally, you may find a few stains on your driveway during the first few weeks of completing this process, but these stains usually wash out fairly easily.

As you can see from the above steps, cleaning the evaporator drain hose is one of the easiest jobs. If you have read these instructions, studied the service manual and decided that you are better off entrusting this service to a professional, entrust the cleaning of the evaporator drain hose to one of AvtoTachki certified mechanics.