What is the primary function of the air compressor in heavy vehicle brake systems?

• A. To provide vacuum for HVAC
• B. To supply compressed air for brakes
• C. To generate electrical power
• D. To cool the engine

Answer: (B)

In heavy-vehicle air brake systems, the air compressor’s job is to generate and supply the compressed air that powers the brakes. It’s driven by the engine and fills the vehicle’s air tanks, building up pressure so the brakes can be applied when you press the pedal. The system relies on this stored air to actuate the brake chambers, making braking reliable even under high demand. The compressor’s pressure is regulated by a governor, which cycles the compressor on and off to keep the tanks within the operating range. The other functions listed—vacuum for HVAC, generating electrical power, or cooling the engine—aren’t the primary role of the air compressor in these braking systems.