cleaning the coils before summer use
It's starting to hot in Texas. I have a refrigerated air window unit in my office so I don't have to cool the whole house down to remain comfortable while answering iFixit questions. It has a removable plastic filter on the inside of the house that can be removed and washed. Behind that are the radiator coils. Those are dirty and I would like to clean them without making a big mess. Does anyone know how to do this and any other yearly maintenance things I need to do before starting it up for the year?
To start use a vacuum cleaner with a soft brush hose attachment to get rid of the loose stuff. Then you are going to want to use a degreaser/ cleaner to spray on the evaporator. I would suggest a foam based one such as this to keep the mess minimal. You may notice the product I suggested is self-rinsing, which means it will only need wiped off. To wipe it off between the fins use a fin comb. Fin combs come in different sizes and styles. To pick the proper one measure the number of fins per inch and purchase one that has the matching comb. Most of those are plastic. I could not find one like mine which is more like a disposable razor with different sized interchangeable blades. I've got 10 combs/blades for mine. Click here for an example of the plastic one I have. They seem to be coming in some kind of a rotating circle set up now. These can also be used for straightening out bent fins. They also make universal fin combs. Please click here for an example. The universal ones do a good job for cleaning ( I have one for that purpose only.), if the fins are not bent, I would not recommend using one to straighten bent fins. You will want a bucket of water and some paper towels for cleaning the comb between strokes.
Insofar as recommended maintenance. Clean and straighten out the inner and outer fins on both the evaporator and condenser. That will ensure good air flow and efficiency. Clean the fan blades and if the fan has an oil port add some oil (3n1 electric motor oil). If you have a clamp on amp meter use it to compare the amperage draw of the unit to the rated amount on the specifications plate provided by the manufacturer, if there is more than a 25% difference you may consider having it professionally serviced - if you are not happy with it's performance. Freon systems are closed systems and if they are leaking it is most likely through a compromised piece of metal or a joint. With age compressor motors do tend to draw less current, so a difference in plate rating and actual current draw does not always indicate a loss of freon in the system. You can do what is called a wet bulb test. Use a quick reacting thermometer where the air is coming in to be circulated. Take another quick acting thermometer, wrap it's sensing part with a wet paper towel, place it where the air is leaving the unit to "cool" the room. Let the AC run for 10 minutes. There should be approximately a 20F difference between the two if the system is in good order.
I don't think it can be done without some mess ... condensation has probably glued the dirt/dust to the coils... Take it outside to brush and wash/rinse with soapy then clean water would be, IMnsHO the best way. if you have to do it inside you might get by with putting down a tarp (or using bathtub/shower stall) and using a hand pump up sprayer (like for liquid weed killer, or deck wash/sealant) to get some pressure behind the water.
These units (all AC units actually) lose freon (coolant) as the molecules are so small they pass through most rubber hoses & seals - that affects efficiency of cooling. Take it, or call an AC specialist to come over, who can run a pressure test and top off the coolant (which also contains pump lubricant).
As always "if this answer is acceptable"... you know what to do.