Fault Phenomenon: Komatsu HD785-7 mining truck air pressure builds slowly, or the air compressor runs under load continuously, causing significant engine power loss.

Troubleshooting Process:
– Checked unloader valve: spool stuck in loading position.
– Checked pressure regulator: air pressure regulator set incorrectly or failed.
– Checked lines: control air line leaking or clogged.
– Checked piston: air compressor piston rings worn.

Root Cause: The air compressor unloader valve is stuck in the closed (loading) position due to sludge accumulation, causing the compressor to continue compressing air even after reaching the upper pressure limit, unable to unload.

Required Parts: Clean or replace air compressor unloader valve and pressure regulator.