Commercial Driver’s License (CDL) Test 2025 – 400 Free Practice Questions to Pass the Exam

A single brake system in a vehicle is likely in need of adjustment when the compressor cuts out between 70 to 90 psi. This is important because the air compressor in a braking system is responsible for maintaining adequate air pressure necessary for the brakes to function properly. If the compressor is cutting out at this pressure range, it indicates a potential issue within the air system, such as leaks or insufficient pressure, which can compromise the effectiveness of the brake system. Ensuring that the compressor operates correctly at the appropriate psi range is crucial for maintaining safe stopping power and overall vehicle safety.

While other symptoms, such as a spongy brake pedal, vehicle pulling to one side, or high-pitched noise, may suggest problems with the braking system, they do not specifically indicate the need for adjustment in the same direct manner as the compressor’s pressure cut-out. They could point toward issues such as air in the brake lines, uneven brake wear, or possible brake component failure, but these conditions may not always mean that an adjustment is required. Observing and addressing the airflow and pressure issues with the compressor is fundamental to ensuring the entire braking system functions effectively.