Final answer:
For air brake systems in good condition, the air compressor should start pumping at about 100 psi and stop at around 125 psi to ensure proper brake function and readiness.
Step-by-step explanation:
The question pertains to the operational characteristics of air brake systems in vehicles, primarily large ones such as trucks and buses that use compressed air to operate the brakes. For air brake systems in good condition, the air compressor, which is responsible for maintaining the necessary pressure in the system, should begin pumping at approximately 100 psi (pounds per square inch) and stop at about 125 psi. This range is crucial for ensuring that the system has enough air to function properly and is ready to respond when the brakes are applied. If the air pressure drops below this range, the air compressor will kick in to restore the proper pressure.
Some advanced air brake systems, such as those used in construction equipment like bulldozers, might integrate a motorized pump to aid the air compressor in maintaining pressure. It is also important to note that due to the compressible nature of gases, air brake lines need to be free of air for the brakes to work efficiently. Any trapped air can cause a spongy brake feel and reduce braking efficiency, which is why the process of bleeding the air is essential for maintaining proper brake functionality.