Fault Phenomenon: XCMG HB58K water pump operates normally when cold. After reaching operating temperature (high water temperature), the water pump stops spinning, and the cleaning system has no water, with no alarm on the dashboard.

Troubleshooting Process:
– Checked water pump motor fuse: fuse intact, not blown.
– Checked water pump mechanical seal: no seizing, rotates freely by hand.
– Checked water pump relay: energizes normally when cold.
– Measured relay coil resistance at operating temperature: found internal coil open circuit.

Root Cause: Poor heat resistance of the water pump control relay coil causes it to open circuit at high temperature.

Required Parts: Water pump control relay.