Before you start
Get an air conditioner wash-bag. Wash-bags are simply used to cover the indoor unit in such a way that enables you to clean it out without making a mess.
Also make sure that the air conditioner is completely shut off from electrical power in order to mitigate the risk of electrocution.
Clean the Condenser Coil
The condenser coil, found in the outdoor unit of a split unit AC (also called the condenser), is one of the more important parts of your air conditioner. Because of its location (in the outdoor unit) the condenser coil will most likely be exposed to dirt and other intrusive objects and will therefore need to be cleaned regularly.
Cleaning the condenser coil is important because if you allow it to get very dirty it will need to consume much more energy in order to function. This will lead to increasing energy costs for you.
To clean the condenser coil, all you have to do is get a brush and some detergent, and simply brush the dirt off with some water.
Clean Condenser Fins
The condenser fins are the metal frame surrounding the central fan of the outdoor unit. The function of the central fan is to suck in air and as such the condenser fins, which act as a sort of shield or filter in front of it, tend to trap a lot of dirt and debris.
You could pick out or brush out the dirt by hand or even hose down the condenser fins.
Change or Clean air filters regularly
Faulty or dirty air filters in the indoor unit of your AC will prevent proper air flow inside the air conditioner, which would invariably lead to decreased efficiency and probably a break down at some point.
Rather than allowing such preventable damage to occur to your AC, be sure to regularly replace its air filters or clean them with a brush.
Clean evaporator coil
The evaporator coil is located in the indoor unit of the air conditioner (also called the evaporator) and is responsible for the actual cooling effect of the AC. The steps for cleaning the evaporator coil are the same for cleaning the condenser coil.
There’s a limit to exactly how much servicing and maintenance you can effectively do on your split unit air conditioner by yourself. At some point you probably ought to call in the pros to take a proper look at the system; however, following the steps outlined here will certainly help a great deal in keeping your air conditioning system functioning just the way you want it to.