How to Service and Clean Your Air Conditioning Coil

When you sweat it evaporates and cools your skin. When you compress something it gets hot. That's how your air conditioner works. There are two coils in your system. One coil is inside and gets cool. The other is outside and gets hot. The both have fans to more large amounts of air through the coils to maintain the temperature of the coil. The refrigerant runs through both coils. It is a gas at room temperature, but can be compressed into a liquid by the compressor motor in the outdoor unit. When it is compressed it gets very hot. The outdoor fan draws fresh air through the coil and blows it out the top of the unit cooling the refrigerant. The compressor will be overworked and draw too much electric if the fan fails or the coil is clogged with dirt. It will pop the breaker or blow a fuse as the condition get worse especially on a hot day in direct sunlight. If there is too much refrigerant in the system it will overwork the unit and cause a fuse to blow. The liquid refrigerant runs through the small copper line to the indoor coil where it expands and turns into gas. It cools the coil as it expands.

The indoor blower circulates air through the indoor coil. The air is cooled as it passed the coil. In a perfect system there should be a 20 degree drop in temperature from one side of the coil to the other. This is called a temperature split. Humidity inside the house collects on the coil like a glass of ice water sweating on a summer day. This dehumidifies the house making it more comfortable. The water is collected in a pan and removed by a drain tube. If the airflow to the indoor coil is reduced the water on the coil can freeze because the coil is so cold. The ice decreases the air flow and begins a downward spiral until the coil turns into a block of ice. The unit can not be serviced until the ice is completely melted.

Air Conditioner Freeze Up

First of all, turn off the unit. I know you don't want to do it, but it must be done. The ice has to melt. If the coil is freezing there might be some frost or ice on the copper line going to the coil. There might be water leaking from the unit because the drain is overwhelmed. There could be little to no airflow coming from the vents. A freeze up can occur when the unit needs freon or there is an air flow restriction. If you need freon then you need to call for service.

An air flow restriction is usually caused by a clogged air filter. It also could be caused by closed or blocked vents, a broken blower motor or a clogged coil. Make sure all of the vents are open and are not obstructed by furniture. Check if the fan is running. Check the filter. If the unit was running without a filter or if the filter was so dirty that it was sucked in, the coil could be dirty. The only way to really be sure is to take out a few screws and peek at the coil or lift the coil case away from the air handler to look inside. Some units are easy to open and some need to be cut open. If your coil is inside of a section of duct work you will have to cut an access door. Systems are set up differently, there are up flow and down flow units. Some coils are under the air handle, some are over it. You need to look at the side of the coil where the air enters. In other words If dusty air is flowing through the coil, the dust will only build up on one side of the coil. You need to look at that side of the coil. A mirror and flash light might be needed. Your coil should look a lot like the radiator in your car. If it's very dirty, it may look like it's covered in felt.

Indoor Coil Cleaning

If you have easy access to the dirty side of the coil you could try to use a vacuum and a paint brush to remove the dirt. Be careful, the fins on the coil will bend very easy. You can buy a chemical coil cleaning solution from a plumbing supply and sometimes at the home store. Follow the instruction on the container and give it plenty of time to work. The cleaner will dissolve most of the dirt. It can take several applications if the coil was extremely dirty. Brush the coil after it is sprayed with the cleaner to help remove the dirt. If it is tight inside the coil case you can tape your paint brush to a stick so you can reach inside. You can use a cheap pesticide sprayer to blast the dirt off of the coil. Most of them work best when you completely unscrew the spray tip. Your sprayer may be different. If you use the sprayer monitor the amount of water you are using. Don't overwhelm the drain. Clean the drain pan or it may clog and overflow. When it's clean reassemble the coil case and run the unit. Do not run it when the duct work is open because you may not get enough air flow through the coil. If it is operating properly you can use caulk or metal tape to seal the panels that you removed.

Outdoor Coil Cleaning

A dirty coil can cause your outdoor unit to blow fuses or circuit breakers. It can also be caused by overcharging the system with freon. If you have not had your unit serviced recently, it should not be overcharged. Outdoor units get dirty from grass clippings, dryer vents and weeds. Before you start make sure you turn off the breaker and/or pull out the disconnect to turn off the high voltage to the unit. Turn off the power even if you blew a fuse. Most of the time only one fuse will blow. The other fuse is still supplying power to the unit.

Use a garden hose to wash the dirt out of the coil. Be careful not to force the dirt further into the coil with a strong jet of water. Try to use the hose at an angle to push the dirt into clumps. A paint brush can help, but do not scrub the coil because you will bend the fins. If you can't wash off the dirt from the outside you will need to remove the top of the unit where the fan is mounted so you can get inside with the hose. Remove the screws that secure the top. Most of the time the fan is bolted to the top, but there should be enough slack in the wires to slide or turn the top out of the way. On some units the corners or side panels will come free when the top is removed. Just make a mental note of how it goes together so you can put it back when you are finished. Use a spray nozzle or your thumb to jet the water from the hose. Start at the top and spray from the inside to the outside because the fan draws the air and dirt in through the sides. It takes time, just work one small area over and over until the muck stops coming out. If it will not come clean use the chemical cleaner. When you are done replace the top ( and sides ), make sure the wires to the fan are secured and nothing can hit the fan blades. Replace the disconnect,turn on the breaker and run the unit. You do not have to wait for it to dry, it gets wet in the rain.