One of the typical reasons why air conditioners do not work properly is a clogged or dirty filter. Follow the manufacturer's recommendations on how often you should change your air filter.
Another simple solution is to make sure that the thermostat is on, that the interior is clean, level, not affected by sunlight, and that it is set correctly.
When refrigerant starts to leak into the air conditioner, the unit will not work properly and the temperature will fluctuate.
Debris, dust, and lint can clog the drain tube, just like the filter. If it becomes clogged, the drain pan fills up and water leaks out and can damage the AC unit or anything around the pan.
Circuit breakers and fuses protect the AC drive motor or compressor from overheating. Often when a motor stops, one of the first parts the HVAC technician checks is the switch.
The motors that drive the compressor and fans won't work if capacitors aren't present. The start capacitor sends a jolt to activate the motor, while the run capacitor provides a series of jolts to keep the motor running.
The compressor applies power to the refrigerant and pushes it through the coils to effect heat exchange. If the compressor is not working, the air conditioning unit will not cool your home.
Evaporator coils absorb heat from the air and return it to the house as cool air through a series of air ducts. Coils can corrode, but if they are indoors, they typically only require maintenance every three years.
The condenser coils are located outside with the compressor so they can get dirty from bad weather. They can usually be hosed down once a year, but if they get too dirty, an HVAC technician will need to clean them with a chemical cleaner.
On an AC unit, there are contactors for the compressor, fan motor, and condenser fan motor. They build an electrical connection that turns on the compressor and motors.