Which one of the following is NOT a part of an air conditioning system?

The water pump is not a component of an air conditioning system. An air conditioning system typically consists of a compressor, receiver-dehydrator, and evaporator, which all play critical roles in the cooling process.

The compressor is responsible for compressing the refrigerant and circulating it through the system. The receiver-dehydrator maintains the proper level of refrigerant and removes moisture from the system, which is crucial for preventing corrosion and ensuring efficient operation. The evaporator allows the refrigerant to expand and absorb heat from the air inside the vehicle, effectively cooling the cabin.

In contrast, the water pump is primarily a component of the engine cooling system. It circulates coolant through the engine and the radiator, helping to maintain the engine's operating temperature. The function and role of the water pump do not intersect with the process of an air conditioning system, which focuses on cooling the air within the vehicle as opposed to controlling the engine temperature.