Home › CDL Practice Tests › Air Brakes Questions › Question 31
What drives the air compressor on most heavy trucks?
- A.The transmission output shaft only when moving
- B.A separate electric motor powered by the trailer
- C.The driver's foot pedal
- D.The engine, through gears or a belt, whenever the engine is running
Correct answer
D. The engine, through gears or a belt, whenever the engine is running
Why
The compressor is engine-driven so it can build and maintain air whenever the vehicle is operating. If the engine stops, no new air is made and the driver must work only with what is stored in the tanks.
Manual topic: Air Brakes - Air Compressor and Governor · From the Air Brakes practice bank (AB-031).