What is the most probable cause of an air compressor delivering below capacity?

When an air compressor delivers below capacity, one of the most probable causes is broken or worn valves. These valves are critical components that control the intake and discharge of air within the compressor. If they are not functioning properly, it leads to inadequate sealing or poor air flow, which directly impacts the compressor's ability to take in or expel air effectively.

Worn valves can prevent the compressor from reaching its intended operational pressure, resulting in a loss of performance and reduced output capacity. The efficiency of the compressor is heavily reliant on the condition of these valves; thus, if they are compromised, the entire system can underperform.

While dirt in the air intake can also restrict airflow, low power supply voltage can affect the motor's performance, and excessive discharge pressure can indicate issues with the system, none of these factors usually have as direct an impact on the airflow and pressure generation as faulty valves do. Therefore, understanding the mechanics of how compressor valves work underscores why a malfunction in this area is a significant reason for decreased output capacity.