Air conditioners can be the most finicky of things. My aircon must be at least 6-7 years old now. I have to have it served every 3-4 months now. The problem for my landlord and I have to deal with are the guys who service the air conditioners. They know that they need to ‘clean’ the air conditioner and gas it.
In reality, they will just clean it with water and then leave. You point to the gas and they just smile. The next time they may put in a little gas but then not clean it. This is to ensure that you will keep calling their service (they think). This results in your aircon using more electricity the pump stays on trying to cool your room. With no gas, it will never reach the desired temperature (26 C for me).
I told my landlord what has been happening. Today the guys did both. It is amazing the difference in temperature immediately after. My room is now a cool 27 C (80 F). Before Before the serviced it, my room was at 31 C (88 F).
My lease ends in January, 2009, so this cleaning should get me there without needing another service call.
In my next house, I will buy my own aircon. The newer air conditioners use less electricity.