a/c

[ckdg0204]

I have a window unit a/c i cleaned the filter and cleaned it out and it still freezes up,any suggestions?

[LazyPup]

The formation of ice on an evaporator coil is indicative of a restriction of air flow through the coil. The leading cause of this problem is a dirty air filter but in this case you have already cleaned the air filter so we will rule that out for the moment.

The outer covering of a window air conditioner serves not only as a housing to protect the machinery, or protect people from getting hurt by the machinery, it also serves as an air duct to direct the air through the coils in the proper manner. Many of the larger window units can be slid out of the covering for servicing, but it is vitally important that it be placed back in the cover before running an operational test. Assuming that you did have the unit in the covering while running we will then move on to the next likely cause of the problem, a dirty coil.

You stated that you cleaned the inside of the unit, but I am assuming here that you brushed it out or perhaps used a vacuum cleaner to remove the dirt, dust and other visible debris. While that is definitely the correct thing to do, non the less, it will not clean the coil sufficiently. During normal operation the coil is cold and moisture from the room air passing through the coil will condensate on the coil. That moisture then drips down the coil to the condensate tray and is discharged out the back of the unit through the condensate drain. The problem is that microfine dust particles that get through the air filter are then caught by the moisture and for a layer of mud on the coils. When the unit is not running that mud will then dry on the coils forming a nearly rock hard covering deep within the fins. In order to clean that out you need a chemical coil cleaner that can be sprayed into the coil fins to disolve that mud out.

In the trade we use a condensed coil cleaning solution that comes in a gallon jug and is then cut about 20 to 1 with water before using. It is highly unlikely that a homeowner would ever have need of a gallon of the concentrate but if you go to an HVAC supply house they also have aerosol cans of ready mixed "Coil Cleaner".

With a little experience and a good drop cloth you can clean the coils with the unit still in the window, but this is a messy job and I would strongly suggest you carry the unit outside before beginning.

Remove the front cover and air filter so you have direct access to the coil.

Read the instructions on the can carefully as not all product work exactly the same way.

Typically you would shake the can of coil cleaner vigorously as you would a spray paint can then begin spraying the liquid into the coil. The liquid will come out of the can in a clear direct liquid stream and you must be sure that you spray the entire coil with it. As the liquid works it will form a thick foam almost like shaving cream. It may also feel a bit hot to the touch and it may even produce a mist that looks like smoke. Do not worry, that is the normal reaction of the product. As it expands into foam the foam then pushes the dirt out of the coils. Once the foam begins to break down again the cleaning action has completed. Normally this will take about 30 minutes.

Some products suggest that you then rinse the coil with water before operating the unit. If rinsing with water is it best to use a very low pressure water flow. The prefered method would be to fill a garden tank sprayer with plain water and use that to rinse the coils. If you do not have a tank sprayer you can use a garden hose but be sure to use a low pressure and misting spray because you don't want the force of the water to distort the shape of the fins. When spraying with a garden hose you may want to wrap a plastic garbage bag around the motor before you begin to insure you don't get the motor wet. Also be very careful not to spray water into the electrical control panel section.

Here is a tip that I often use. If you suspect that you did get water into the electrical section get an old jar lid like a mayonase jar lid. Fill the lid about 1/2 full of water and set it on top of the AC unit, then leave it set out in the sun. Once the water in the jar lid has evaporated you can assume that any water in the control section would have by now evaporated as well, so you can then set the unit back in place and begin running it.

In most cases cleaning the coil in this manner will resolve the icing problem. If by chance the unit does still continue to ice up, the problem is then a low refrigerant charge and would require a trained and certified HVAC tech to install tap valves and charge the system. Either way you have not lost anything by cleaning the coils because it is technically impossible to charge a unit unless the coils are clean, so you just saved the cost of having the tech do that job.