According to HofStuffWorks, troubleshooting a central air conditioner starts by identifying the problem. These may include the unit not working, not stopping or not cooling.
When the unit is not working, HofStuffWorks.com suggests checking for blown or tripped fuses. According to About.com, another reason for the condenser not working can be the thermostat set too high. It suggests lowering the thermostat temperature by five degrees.
If the unit is constantly running, it is best to turn the thermostat up by a few degrees. If that does not work, the unit can be cleaned from the inside using a vacuum. A couple of drops of oil on the motor might also help, according to HowStuffWorks.com.
If the unit is not cooling at all, the condenser unit might be dirty or blocked. Evaporator blockage can also cause the unit to stop cooling. The condenser and fins can be washed using a garden hose. Blockages like weeds, debris or vines should also be removed.
If inadequate cooling is paired with a long or constant on cycle, it can be a sign of a worn-out condenser, according to About.com. When the manual troubleshooting does not achieve results because of malfunctioning or broken parts, the help of a professional technician may be required.