North Carolina CDL Air Brakes Practice Test

In an air brake system, the primary function of the air compressor is to build and maintain air pressure necessary for the operation of both service and parking brakes. If one air compressor malfunctions, the ability to build or maintain pressure is compromised, which can lead to a complete loss of functionality in both systems. Without adequate air pressure, the vehicle will not be able to operate its braking systems effectively, posing a serious safety risk. This situation highlights the critical importance of having a properly functioning air compressor in maintaining braking system reliability. While there may be redundancies in certain systems, without the ability to generate and sustain air pressure, the brakes will not operate as designed. Therefore, the correct understanding is that a malfunctioning air compressor prevents the air brake system from building or maintaining necessary pressure, making option C the accurate choice.