The air compressor will stop pumping air to the air brakes at what pressure?

The air compressor will stop pumping air to the air brakes at what pressure?

• A. 125 psi
• B. 110 psi
• C. 135 psi
• D. 150 psi

Answer: (A)

Air brake systems use a governor to turn the compressor on and off as the system pressure changes. The compressor stops pumping when the system reaches the cut-out pressure, which for most trucks is about 125 psi. This stopping point keeps the air tanks from over-pressurizing and provides a stable reserve for braking. When the pressure falls to the cut-in level, usually around 100–110 psi, the governor allows the compressor to start again to recharge the tanks. So 125 psi is the pressure at which the compressor stops pumping.

Air brake systems use a governor to turn the compressor on and off as the system pressure changes. The compressor stops pumping when the system reaches the cut-out pressure, which for most trucks is about 125 psi. This stopping point keeps the air tanks from over-pressurizing and provides a stable reserve for braking. When the pressure falls to the cut-in level, usually around 100–110 psi, the governor allows the compressor to start again to recharge the tanks. So 125 psi is the pressure at which the compressor stops pumping.