AIR SYSTEM 5. Start the engine and build up the air pressure again. Air Compressor Operation 6. Stop the engine, and apply the brakes fully. Apply the brake pedal and hold it down for five minutes. The pressure drop should not exceed 3.0 psi (21 kPa) per minute. All compressors, regardless of make or model, run continuously while the engine is running. System pressure is controlled by the governor. The governor acts in conjunction with the unloading mechanism in the compressor cylinder block to start and stop compression of air. The compressor is unloaded when the system pressure reaches 120 psi (827 kPa) and compression is reestablished when system pressure falls to 100 psi (690 kPa).
Secondary Air Pressure Gauge Follow the procedure below to check the compressed air system for leaks: 7. If you detect excessive leakage (air pressure loss greater than 3.0 psi (21 kPa) after five minutes of brake application), a leakage test should be made at the air line connections and at all air brake control units. These tests should determine where air is escaping. 1. Periodically, or after maintenance or replacement of air system components: 2. Build up air pressure in the system to the governor cutout point or until 120 psi (827 kPa) is reached. 5 3. Stop the engine and release the service brakes. 4. Without applying the brake pedal, observe the rate of air pressure drop.
This rate should not exceed 2.0 psi (14 kPa) per minute. 5-64 Y53-6077-1B1 (03/17)