Turn off your air conditioner, get a garden hose, and spray the coil using an up-and-down pattern. Be particularly attentive if your condenser is close to a dryer vent, or if your neighborhood is full of cottonwood trees. These two items are "air conditioner killers". This simple step alone can increase the efficiency of your air conditioner. It will also run less, increasing the life span of your equipment.  A good sign that your filter needs changing is the fact of ice forming inside your inside cooling unit (evaporator section). This may be difficult to see as the unit is sealed, but touch the outside metal and feel for a noticeable temperature difference. You may also see ice on the large line going to the outside unit (suction line). If ice is forming, it is possible that your air filter is severely dirty and restricting your normal air flow. This allows ice to form due to the fact that not enough heat is being introduced to your cooling section.
اغسل لفائف المكثف مرة واحدة في الموسم أو كلما تطلب الأمر. نظف المُرشح أو غيره باستمرار.