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Air Brake Compressor and Governor Flashcards

6 cards from real CDL AIR BRAKE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the primary function of the air compressor in an air brake system?

    Answer: To pump air into the storage tanks

    The air compressor pumps air into the storage tanks to maintain system pressure needed for braking.

  2. At what pressure does the governor typically cut out the air compressor?

    Answer: 100–125 psi

    The governor cuts out the compressor at around 100–125 psi to prevent over-pressurization of the system.

  3. At what pressure does the governor cut in and signal the compressor to resume pumping?

    Answer: 80–85 psi

    The governor cuts in at around 80–85 psi, signaling the compressor to resume pumping air.

  4. What is the purpose of an air dryer in the air brake system?

    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.

  5. How is the air compressor typically driven on a commercial vehicle?

    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.

  6. What can happen if the air compressor governor fails in the open position?

    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.

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Sources & references

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  1. dol.wa.gov — Test delivery, exam format, registration, score validity · verified Nov 2026
  2. ecfr.gov — Test delivery, retake policy, eligibility, passing score · verified Nov 2026
  3. dmv.ny.gov — Fees, retake fee · verified Nov 2026
  4. dps.texas.gov — Test delivery · verified Nov 2026