CDL Air Brake Air Brake Compressor and Governor 1 — Questions and Answers
Question 1: What is the primary function of the air compressor in an air brake system?
- To pump air into the storage tanks (Correct answer)
- To release air from the brake chambers
- To control the governor cut-out pressure
- To pressurize the brake pedal
Correct answer: To pump air into the storage tanks
The air compressor pumps air into the storage tanks to maintain system pressure needed for braking.
Question 2: At what pressure does the governor typically cut out the air compressor?
- 60–80 psi
- 100–125 psi (Correct answer)
- 150–175 psi
- 200–225 psi
Correct answer: 100–125 psi
The governor cuts out the compressor at around 100–125 psi to prevent over-pressurization of the system.
Question 3: At what pressure does the governor cut in and signal the compressor to resume pumping?
- 20–40 psi
- 50–60 psi
- 80–85 psi (Correct answer)
- 100–110 psi
Correct answer: 80–85 psi
The governor cuts in at around 80–85 psi, signaling the compressor to resume pumping air.
Question 4: What is the purpose of an air dryer in the air brake system?
- To cool compressed air
- To remove moisture and contaminants from the air supply (Correct answer)
- To increase system pressure
- To store compressed air
Correct answer: To remove moisture and contaminants from the air supply
The air dryer removes moisture and contaminants from compressed air to prevent water buildup and freezing in the system.
Question 5: How is the air compressor typically driven on a commercial vehicle?
- By an electric motor
- By the vehicle's engine via belt or gear (Correct answer)
- By hydraulic pressure
- By the transmission output shaft
Correct answer: By the vehicle's engine via belt or gear
The air compressor is driven by the vehicle's engine through a belt or gear connection.
Question 6: What can happen if the air compressor governor fails in the open position?
- The compressor will stop working entirely
- Air pressure will drop to zero
- The compressor will run continuously and may over-pressurize the system (Correct answer)
- The brakes will lock up automatically
Correct answer: The compressor will run continuously and may over-pressurize the system
If the governor fails open, the compressor runs continuously and can over-pressurize the system, potentially damaging components.
CDL Air Brake Air Brake Compressor and Governor 1
What is the primary function of the air compressor in an air brake system?