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CDL · General

What does the air brake governor control?

Correct answer

When the air compressor pumps air into the reservoirs (cut-in and cut-out pressures)

  1. A The steering
  2. B When the air compressor pumps air into the reservoirs (cut-in and cut-out pressures)
  3. C The engine speed
  4. D The headlights

Why this is the answer

The GOVERNOR controls when the air compressor PUMPS air into the reservoirs — it stops the compressor from pumping (CUT-OUT) when pressure reaches the maximum (around 125 psi) and starts it again (CUT-IN) when pressure drops to the minimum (around 100 psi). ASVAB/CDL air brakes. This maintains air pressure within the proper operating range automatically. The governor prevents over-pressurization and ensures enough air is always available. Knowing the governor controls the compressor's cut-in and cut-out (maintaining the air pressure range) is commonly tested.
Source: FMCSA CDL Manual — Air Brakes, Governor

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