Home Improvement Skills & Specialties HVAC

How to Clean Air Conditioner Coils

Lee Wallender

Published on 04/22/22

Reviewed by

Deane Biermeier

Cleaning Air Conditioner Coils — CRobertson / Getty Images

Project Overview

Total Time: 30 - 45 mins

Skill Level: Beginner
Estimated Cost: $10 to $25

Cleaning your air conditioner coils is, without a doubt, the simplest and lowest-cost way to improve your A/C's efficiency, durability, and lifespan. It also enhances indoor comfort and saves on operating and repair costs.

These benefits make cleaning your A/C coils a task you should do without fail each year. After the initial learning curve of cleaning the coils, subsequent cleanings will go much faster and easier.

Understanding Air Conditioner Coils

The cool air that flows from your central air conditioning system is the result of two sets of coils that do different things: condenser coils that dissipate the heat and evaporator coils that cool the air. Both sets of coils need to be cleaned.

Condenser Coils

Located outdoors
Found in the condenser unit
Can be hosed down
Dirty from outdoor contaminants: leaves, dirt, pollen, tree fluff, etc.

Evaporator Coils

Located indoors
Found in the air handler
Cannot be hosed down
Dirty from indoor contaminants: dust, hair, animal fur, etc.

Condenser Coils

Condenser coils are located in the condenser, a large metal outdoor unit. Condenser coils remove and dissipate hot air from the house.

Condenser coils are metal tubes that run through aluminum fins. Refrigerant in gas form is compressed into the coils, where the gas is condensed into a hot liquid. The condenser coils and fins dissipate the heat as the liquid travels through the coils. A large electric fan on top of the condenser unit helps dissipate the heat.

Tip

Condenser coils never become cold. Instead, they act like a sponge to soak up indoor heat and move it outside.

Evaporator Coils

Evaporator coils are located indoors near the air handler. Evaporator coils become very cold. Blower air passing through the evaporator coils sends cool air into the house.

Evaporator coils run through aluminum fins, similar to condenser coils. Once the refrigerant has passed through the condenser coils, it moves indoors to the evaporator coils. As the refrigerant liquid enters the coils, it expands into a gas and cools down the coils.

When to Clean Air Conditioner Coils

Clean air conditioning coils once a year. If you frequently use your A/C or if you have a dirty exterior (leaves, pollen, and dirt) or interior, clean the coils more frequently or on an as-needed basis.

Clean the coils in the spring and possibly once again in mid-summer.

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Why It's Important to Clean Air Conditioner Coils

Once you know how to clean air conditioner coils, you'll be able to improve the system's efficiency, minimize wear, reduce service technician calls, and save money.

Improve Cooling Efficiency

When they are dirty, the condenser fan and compressors work increasingly harder just to output the same amount of cool air to the home. Cleaning the coils restores them to their original state so that they can work at their intended capacity.

Minimize Wear on System

Dirty coils mean that the system cycles on more frequently to maintain the temperature set-point. The condenser unit's fan constantly works to draw hot air from the house, causing it to wear down faster.

Reduce Service Calls

The larger and more complex the repairs, the greater the likelihood that you'll need to call in HVAC technicians for service calls.

The average HVAC service call cost is $100 to $200. That's just the cost to show up. Labor beyond that point, plus materials, are all extra. Keeping the system clean reduces the number of service calls you'll make.

Save Money

Air conditioners use a lot of expensive electricity to run. Reducing the frequency and length of run times saves money. Plus, maintaining the A/C system may prevent you from having to eventually purchase a new system—an expensive proposition that starts at around $3,000 to $4,000.

Safety Considerations

Coil cleaner is a health hazard. Use safety glasses, a face shield, chemical-resistant gloves, and chemical-resistant clothing. Most A/C units are located outdoors and should have sufficient ventilation for working with coil cleaner. If you do not expect adequate ventilation, use a NIOSH mechanical filter/organic vapor cartridge in a respirator.

Air conditioner condensers are highly charged 240V systems. Make sure that electricity is completely disabled before working on the condenser.

Equipment / Tools

Cordless drill
Screwdriver
Fin repair comb
Nylon scrub brush
Bucket
Gloves
Shop vacuum
Vacuum extension wand
Water spray bottle
Flashlight
Garden hose
Sprayer

Materials

2 Cans foaming A/C condenser coil cleaner

How to Clean Air Conditioner Condenser Coils

Locate the A/C Condenser Unit

The condenser unit will be found outdoors, often on the other side of the wall from the electric service panel.
Disable the Electric Breaker

Disconnect the electric breaker that controls the air conditioner unit. The electric breaker will be a small metal box on the side of the house, connected with an electrical whip (cord) to the AC condenser unit.
- Cartridge-style breakers with fuses may pull straight out to disconnect the system.
- Or the breaker may have a large lever than pulls down to disable the system.
- In other cases, a double circuit breaker in the home's electric service panel controls the AC condenser unit.
Warning

Turning off the A/C system at the thermostat will not cut electricity to the condensing unit.
Remove Top and Side Condenser Covers

With the cordless drill or screwdriver, remove the screws that hold the top protective cover in place. Bag the screws and set the bag safely aside. Repeat the process for the side covers and/or protective grilles.
Unscrew the Condenser Fan Assembly From Unit (Optional)

This step is optional and may depend on your condenser model. Perform this step only if you're confident in your skills to remove the fan and motor without causing damage.

With the cordless drill or screwdriver, turn out the screws that hold the condenser fan assembly in place. Bag the screws and set the bag safely aside.

With some units, the condenser fan assembly's wiring harness can be unsnapped from the unit's wiring, allowing you to completely detach and set aside the condenser fan assembly.

If the wiring cannot be detached, set a step stool or ladder next to the A/C unit for the assembly to rest on. Gently pull any excess wiring out of the unit to set the assembly on the stool or ladder.
Inspect the Inside of the A/C Unit

With the unit open, take the opportunity to briefly inspect the condition of the unit inside the cabinet for obvious problems like loose wires, cracked or broken pipes, or advanced corrosion. Call a service technician for any repairs.
Remove Large Debris

Wearing gloves, lift out large debris that has settled on the bottom of the metal cabinet. Leaves, dirt, bark, mulch, pebbles, and grass clippings routinely collect at the bottom of cabinets over time. Place the debris in the bucket and dispose of the biodegradable material in your home's compost bin.
Clean With a Shop Vacuum

Attach the extension wand to the shop vacuum. Vacuum out the remainder of the debris from the bottom of the A/C cabinet.
Fix the Fins

The soft aluminum fins on the heat exchanger are easily crushed. With the metal-tined fin comb, straighten out small areas of crushed fins. Insert the tines of the comb in the fins and move the tool up and down.

Tip

Don't expect to return the fins to like-new condition. Repairs to crushed fins with the comb are generally imperfect but should be better than before.
Clean the Protective Grille

On the outside of the A/C unit, remove any large debris that may have been trapped between the protective grille and the aluminum fins. Leaves tend to become trapped here and should be removed by hand.
Check the Fins With a Light

Hold a strong flashlight or shop light inside the A/C cabinet. Point the light source from the inside toward the outside. While standing on the outside, examine the light source through the A/C fins to gauge the cleanliness of the fins.

Tip

Most of the heavy debris on the fins will be on the outside. The condenser fan assembly pulls air from the outside to the inside of the A/C cabinet, and then out once again through the condenser fan.
Spray the Foam Coil Cleaner

Spray foaming A/C condenser coil cleaner on the inside of the cabinet. Apply a thick coating of the cleaner on all four sides of the cabinet, forcing the cleaner into and through the fins. Do not touch the fins.

Let the foaming coil cleaner and water do the work. Avoid as much physical contact with the fins and coils as possible.
Spray the Inside With Water

Let the coil cleaner sit for 5 to 10 minutes. From the inside out, spray water with the garden hose and sprayer attachment. Keep the spray on wide to avoid damaging the fins. On one side, start at the top and work downward. Complete the side before moving onto an adjacent side.
Spray the Outside With Water

Debris forced out of the fins, cabinet, and grille may cling to the outside. With the sprayer on fine/wide spray, hose the cabinet from the top down. Be careful not to direct the water inward as this may force the debris may into the fins and coils.
Reassemble the Unit

Leave the power off and the condenser unit open until it is completely dry. Then replace the fan (if removed), the side covers or grilles, and the top. Turn the system back on.
Keep the Unit Clean

Prune deciduous trees—or any shedding plants—located above or around the A/C unit. Keep this foliage trimmed back at all times of the year.

Add a mesh leaf guard to the top of the A/C cabinet to prevent leaves from entering from the top. Tie the guard securely to the cabinet with the included bungee cords.

How to Clean Air Conditioner Evaporator Coils

Cleaning the evaporator coils is a modified version of cleaning the condenser coils. Since evaporator coils are indoors, it's not possible to hose them down with a garden hose. Instead, use a spray bottle to control the water discharge.

Shut Off the Power

Turn off power to the A/C system at the electric service panel.
Locate the A/C Evaporator Coils

Indoors, evaporator coils will be found on the supply side of the A/C system behind an access door. Open the door by removing the screws.
Inspect the Coils

The evaporator coil assembly is shaped like an "A." The inner section of the assembly will be the dirtiest side.
Brush the Coils

With the nylon brush, brush the aluminum fins in the long direction of the fins. Start at the top and work downward. Let the debris fall to the bottom. Occasionally, vacuum up the debris, taking care not to jostle or damage the fins.
Fix the Fins

If any fins have been flattened, use the fin comb to straighten them out again.
Spray the Foam Coil Cleaner

Spray foam coil cleaner on the inside of the evaporator coil assembly. Spray a generous amount of cleaner.
Rinse the Coils

After about five minutes, carefully rinse down the coils with clean water in the spray bottle. Be careful not to apply too much water. Remove excess water with the shop vacuum in wet mode.

Tip

Because you cannot soak the evaporator coils as you did with the condenser coils, it's better to lightly repeat the process several times than to attempt to clean all at once.
Reassemble the System

Leave the access door open until the evaporator coils are thoroughly dry. Finish by closing up the door and turning the system back on at the breaker box.

When to Call a Professional

Call an HVAC service technician to repair extensively damaged fins, as they cannot be fixed with the fin comb. If you're uncomfortable cleaning either set of air conditioner coils, technicians can do this for you since this is part of a regular maintenance schedule.