At what psi should air compressor governors cut-in?

• A. 75 psi
• B. 85 psi
• C. 95 psi
• D. 105 psi

Answer: (B)

The correct answer is 85 psi because this is the standard cut-in pressure for air compressor governors in commercial vehicles, including school buses. When the air pressure in the system drops to this level, the governor activates the air compressor to replenish the air supply in the system. This is crucial for maintaining proper brake function and overall safety, as the air brake system relies on compressed air to operate effectively. Understanding this is important for drivers and mechanics to ensure that the air brake system is always operating within the required pressure ranges, thereby preventing potential failures or issues while driving.

Other pressures listed might be found in different contexts or systems, but for typical school bus operations and standard regulations, 85 psi is the accepted cut-in pressure for optimizing performance and safety in air brake systems.