Air conditioning maintenance is a very important part of keeping your system running at peak performance and efficiency. Before you begin any maintenance on your unit, there are some hazards to be aware of. The main hazard is electricity. Most air conditioners run on 230 volts and you must be aware of how to turn this power off to the outdoor unit - either by a electrical disconnect that should be located at the outdoor unit or the breaker in the electrical panel of the house. If you are unsure how to turn off the power, please consult with a professional who can assist.
After the power is turned off, the first step in a/c maintenance is to start at the furnace. Turn the switch off, check and replace the furnace filter. A dirty or plugged furnace can starve a cooling coil of the air it needs to cool the house, and a dirty filter can cause the indoor coil to frost and form ice on the coil that can eventually harm the outdoor unit.
Now that the indoor unit is turned off, the air filter is checked and changed and all of the power is shut off, proceed to the outdoor unit. You will need to inspect the outdoor coil for cleanliness. Dirt, grass, cottonwood, leaves, or anything else that could get stuck in the coil must be removed. A typical household garden hose will usually handle this task by rinsing the coil from top to bottom. You can also remove the top cover of the unit to remove debris by spraying the coil from the inside out, this would be the preferred method. Once the coil is clean, reassemble anything that was taken apart and let the system sit for about 30 minutes before you restore power to the unit.
After power is restored the system can be used as normal. If the performance is still questionable then consult with a professional and they can take the next step to check the refrigerant.