Air Conditioner Evaporator [Detailed Guide & Solutions]

An air conditioner evaporator plays a vital role in the cooling function. If the evaporator becomes faulty or clogged, the air conditioner will no longer function as it should.

Air Conditioner Evaporator Coil Clogged – Quick Fix

There are two ways the evaporator coil in an air conditioner clogs. One is with dirt and two is with ice. Typically, the air flows through the air filter before it reaches the evaporator coil inside the indoor unit. But if the filter is dirty, it will transfer some of the dirt to the evaporator and cause it to become grimy. If the evaporator is dirty, you need to clean it. 

How to Clean the Evaporator Coil in an Air Conditioner

Disconnect the air conditioner from electric power and locate the evaporator coil in the indoor unit. That will mean opening the front panel or grille and removing it completely if possible. Next, get a can of compressed air and spray it over the coil to remove stuck dust and dirt. 

If there are stubborn pieces of debris, get the can’s nose closer, position it at an angle of ninety degrees, and spray to remove them. Ensure you protect your mouth, nose, and eyes throughout the process, and spray the dirt into the air conditioner’s ductwork.

Use a small brush to remove any remaining dirt. You will usually find some stuck in places that are hard to reach. Clean with the brush, making sure to use just enough force to dislodge the dirt without damaging the fins. Remove as much dirt as you can while the coil is dry. If it gets wet at any point, it will be much harder to free the dirt.

Get an evaporator coil foam cleaner and spray it on the coil. You will find it in stores, but if not, you can use mild soap mixed in water for the same purpose. Spray the mixture on the coil and allow it to settle for a bit. Then, use the brush to clean the loosened dirt from the coil. Do it gently to avoid spreading dirt to other parts or damaging the fins.

If the evaporator coil is significantly dirty, rinse the cleaning brush under running water from time to time. Continue cleaning the coil until all the dirt is gone. But if the cleaning process is too complex and you are unsure of doing it yourself, it is best to use the services of a qualified HVAC technician.

When the Evaporator Coil Is Frozen

If dirt is not clogging the air conditioner’s evaporator coil, it may be frozen. Dirt is the primary reason it freezes because it acts as an insulator to keep the cold air trapped. First, remove the air filter, place it under running water, add some mild detergent, and wash it. 

Ensure it is still in good working condition before putting it back into the air conditioner. Then, turn off the unit and leave it off until the ice on the coil melts. Clean off any excess water and turn on the air conditioner.

How Does an Air Conditioner Evaporator Coil Work?

When you turn on an air conditioner, the compressor draws the refrigerant while it is still in the low-pressure and liquid state through the tubing in the evaporator coil. Before the refrigerant flows to the compressor, it goes through the expansion valve and this reduces the pressure in the refrigerant, causing it to cool.

The refrigerant leaves the valve and when it does, it is now cold. The valve also controls how the refrigerant flows to the evaporator in order to improve the energy efficiency of the air conditioner. As the refrigerant flows to the evaporator coil, the warm air in the room flows over the coil with the help of the circulation fan. 

And as the air passes over the coil, the refrigerant in it absorbs the heat and leaves the air cold. The moisture in the warm condenses when it touches the cold coil and flows out of the air conditioner through the drain pipe. That way, it also reduces the humidity in the room. Finally, the now-hot refrigerant flows out of the evaporator coil into the condenser, where the heat dissipates into the atmosphere.

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Air Conditioner Evaporator Bad – What to Do

If you suspect the evaporator of your air conditioner is damaged, the first step to take is to turn off the air conditioner. Contact an HVAC technician to examine the coil and determine whether or not it is bad. If it is, you may have to replace the entire indoor unit.

There are a few signs that the evaporator coil is bad. One is a reduction in the flow of cold air. Typically, several other reasons can cause this issue, but a damaged evaporator coil is one of them. Ensure the correct mode of operation and temperature is set in the air conditioner. And if the cooling production continues, look for other signs.

Another clear sign that the evaporator is no longer working is the smell of refrigerant. Under normal circumstances, the gas should not leak because the air conditioner operates using a closed system. The only reason you smell refrigerant, which is typically odorless, is because enough of it has leaked out. So if there is a smell of refrigerant inside the house, it means a significant amount has leaked from the system through the coil.

When the temperature fluctuates while the air conditioner is running, it may indicate evaporator damage. This issue may not be because of a leak in the sealed system but because os some other damage. And if the compressor has a hard time activating or does not activate at all, you may want to check the coils. A leak results in pressure reduction, which reduces the compressor’s ability to circulate refrigerant in the sealed system.

Note: You will notice the same signs in your car’s air conditioning system if you suspect it has a bad evaporator. In such a situation, take the car to an auto technician for repairs.

Mold on Air Conditioner Evaporator Coil

The first step is to clean the mold off the coil before looking for a permanent solution to the problem. Disconnect the air conditioner from electric power and turn off the breaker. Get a container of an evaporator coil cleaner, the no-rinse type, and keep it handy. Next, remove the front panel over the air filter and evaporator in the indoor unit. You may need to remove some screws and bolts, depending on the model.

After that, inspect the coil to locate the areas where the mold is growing. Now, take the container of cleaner and thoroughly shake it. Next, spray the affected area and saturate them. Allow the cleaner to cover the entire area and leave them that way. The cleaner does not need rinsing; the foam will eventually dissipate and the condensation from the coil will wash it off if necessary.

However, if your air conditioner is the type with an evaporator coil that does not form condensation, you may want to rinse it with water. You may also choose to wipe the foam off if you are not comfortable leaving it on the coil. Afterward, check the area to see if the mold remains, and repeat the cleaning process as necessary. Lastly, replace the air filter and front panel, and turn on the air conditioner.

Possible Causes

Water storage in the air conditioner is the primary cause of mold growth. Typically, the air conditioner should automatically drain condensate while it runs. So, if water does not flow out, it must be because the drain pan or pipe is clogged.

Therefore, check the drain while cleaning the evaporator coil. If you find standing water in the pan, it means the drain is obstructed by debris. Use a wet/dry vacuum to clear the drain and ensure water passes freely through the pan into the drain pipe. If you cannot get a wet/dry vac, use a solution of water and bleach or vinegar to clear the drain. Ensure the solution freely flows before closing the drain.

It is crucial to check the drain and pan from time to time to ensure water does not back up into the air conditioner. It also helps to clean the unit regularly because dirt can also cause mold growth. Mold is dangerous to health and can spread to other parts of a house. Regularly cleaning will help you catch any growth or other issues before they become irreparable.

Air Conditioner Drain Pan Leak – Solved

If you find that the drain pan of your air conditioner is leaking, the first thing to check is the drain line. A clogged drain line will only cause water to fill and overflow the pan, making it appear as if it is leaking. Clear the drain with a shop vacuum and try running the air conditioner again.

If the leak continues from the pan, it may be because it is cracked. Such a drain pan cannot hold condensate from the air conditioner, and it will leak out. The only repair for such a problem is to replace the drain pan.

Sometimes, a damaged condensate pump causes the pan to leak. Not all air conditioners have a condensate pump, so it may not apply to yours. But if it does and it is damaged, it may cause an overflow of water and leak not only from the pan but also from other parts and may damage furniture in the long run. Contact an \hvac technician for further assistance.

Air Conditioner Evaporator Fan Not Working – How to Fix

There are a few steps to take if the indoor circulation fan of your air conditioner is not working.

1. Check the Fan Motor

Disconnect the air conditioner from electric power and turn off the circuit breaker. Remove the front panel of the air conditioner’s indoor unit. How you do it will depend on the type of unit. Take the air filter out and inspect the fan behind the evaporator coil. Manually turn the blades to check for stiffness.

If they do not turn well or are broken, replace them and check the motor. Worn bearings or a fault can cause the blades not to function well. Run a continuity test on the motor using a multimeter and replace it if you find no continuity.

Another possible cause of the defective motor is a faulty breaker. It may not be delivering enough voltage to the unit for the motor to run. Parts that turn usually need a lot of power to run. So, hire a technician to check the motor and determine whether the breaker needs to be fixed.

2. Check the Air Filter

Dirt blocks air from flowing through the filter. That is one reason you should always check and clean the filter. Typically, you should clean it every two weeks, but if it must go beyond that, it must not be more than one month.

Remove the air conditioner’s filter and thoroughly wash it with mild detergent and warm water. Ensure you clean it until there is no dirt left. Rinse and dry it with a lint-free cloth, and leave it out to dry. Then, put it back into the indoor unit. Regularly cleaning the filter keeps the evaporator from getting clogged with dirt. A dirty coil will freeze as cold air becomes trapped in it for a long time.

3. Check the Run Capacitor

Another part to check is the capacitor. This component is usually easy to check because when it gets faulty, it may leak oil, bulge, corrode, or rust. Therefore, a simple inspection will inform you whether or not you need a new capacitor.

But if the capacitor is not visibly damaged, you may want to test it for continuity. Get a multimeter and place its test leads on the capacitor’s terminals. Check the unit’s specification sheet for the correct values from the capacitor. If the result from the test does not match the sheet, consider replacing the component.

It is important to note that a capacitor needs to be discharged before testing. It is a complex process that requires a trained technician; the process usually involves live voltage. Doing it yourself can be dangerous, especially if you have never gone through the process.

4. Check the Control Board

Inspect the electronic control board if the motor, filter, and capacitor are not the source of the problem. There are usually small black fuses on the board and you should check them; they are called relays. They operate the circuits of the compressor and fan motor so if they become faulty, the fan may not run.

Using a multimeter, test the voltage output or continuity from the relays. If they are insufficient, the motor of the fan will not run, causing the fan to stop working. So, replace the control board if they fail the test. The same applies if the processor circuitry or onboard relay is malfunctioning. You may need the services of a technician to do a more thorough job.

What Is the Difference Between an Air Conditioner Evaporator and Condenser?

The primary difference between an evaporator and a condenser in an air conditioner is the function each one has. An evaporator coil is where the cold refrigerant flows to and absorbs the heat from the room’s warm air. On the other hand, the condenser is where the now-hot refrigerant flows to and dissipates the heat it carries. In simple terms, the evaporator is the unit’s cold end while the condenser is the unit’s warm end.

Air Conditioner Evaporator Coil Leak – Quick Fix

A leaking evaporator coil in an air conditioner does not have any other repair option than to replace the coil. If that does not apply, you may have to replace the indoor unit or the entire air conditioner. It is pretty difficult to locate leaking points on an evaporator coil because of its location and intricate design.

Causes of Evaporator Leaks in an Air Conditioner

Whether or not your air conditioner evaporator coil is leaking water or refrigerant, the cause of the leak is mostly the same. Volatile organic compounds and high humidity combine to make formic acid which causes corrosion on the copper manufacturing material of the coil. The volatile compounds are gases that come primarily from many household agents such as paint, cleaning agents, dry cleaning, and air fresheners.

Biofilms and mold growth can also cause the coil to spring a leak. Over time, they affect the copper material of the coil, eroding it, and causing a leak. Mold and biofilm are always potential risks with air conditioners and other refrigeration systems. Therefore, it is necessary to keep an eye out for them.


Try using an energy recovery ventilator. It allows fresh air into the house when the weather is cold and removes bad air without affecting energy consumption. What it does is to make the air better by reducing the presence of volatile organic compounds.

Take steps to reduce these compounds in your house. Use household agents that do not emit so much gas on the coil, and if you must clean the evaporator coil, use appropriate agents. In addition, ultraviolet lights will help to prevent the growth of mold and other bacteria. That way, it eliminates corrosion in the long run.

How to Replace an Air Conditioner Evaporator

Typically, you should not replace the evaporator coil yourself if it stops working. It is always best to use the services of a qualified technician. But if you want to do the replacement job yourself, do the following:

Disconnect the air conditioner from electric power and turn off the breaker. Remove leftover Freon from the compressor and turn the liquid line off. Then, lower the switch at the gauge. Next, cut the compressor off to begin removing the coil; this part is pretty tricky and you may need some help.

Check the low side and shut off the valve when the pressure drops to 0. Now is the time to cut the compressor; if you run it with no gas coming in, you will damage it. Using a cutter, cut the lines and tubing that lead from the compressor to the evaporator. Then, pull the coil out.

Next, carefully put the new evaporator coil in place of the old one and solder the cut lines and tubing. But do not open the lines yet; go to the compressor shut-off valve open by the condenser and put a vacuum by its side. Run the vacuum and check the levels; if the vacuum moves, there may be a leak but if not, proceed with the installation.

Now, close the gauges to help the system maintain its vacuum. Start the air conditioner and open the liquid line. Also, open the gas tubing that feeds to the compressor and allow both lines to operate for about ten minutes. Do not purge the system at this point. If everything runs smoothly, you are good to go. But if you are unsure of doing the job yourself, hire a technician for further assistance.


Part of maintaining an air conditioner is checking the evaporator coil. An air conditioner evaporator coil plays a vital role in the cooling process. Therefore, cleaning it and other surrounding parts keeps it from getting clogged, frozen, corroded with mold, or damaged.

The job should be the job of a professional, but sometimes, you may want to do it yourself. Follow this guide to clean and maintain the evaporator, and replace it if necessary. You will also find resources on how to fix a leak or replace the evaporator. If you have a warranty, do not work on the unit yourself.

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