There are multiple components to your heating and cooling system. Some systems contain all of the components in one very large unit, but, in Arizona is is more common to have a split system. The condenser contains a large fan to blow air through the hot coil and to keep the unit cool and is located outside. It also contains a weather-resistant compressor, which keeps the refrigerant moving. The advantage to split system air conditioning is that there is reduced noise inside the home and, since the unit is much larger than a window air conditioner, it is more economical.
Due to the fact that the condenser is outside, it is naturally subject to the elements. This is why it needs to be maintained regularly. Overgrown grass, weeds, or vines should be trimmed so that they do not block the flow of air. This is also true for the light-gauge aluminum fins on the side of the unit. They can accumulate a fair amount of dust and dirt. They can be cleaned using a fin comb and coil cleaner, which are available at most refrigerator supply stores.
If your condenser unit stops working correctly or efficiently, it may be because it needs to be cleaned, or it may be an internal problem, perhaps with the AC compressor. Rainforest Plumbing & Air technicians are trained to repair and/or install condenser units.