Fault Phenomenon: SANY SYM5353THB starts normally when cold. After reaching operating temperature (water temp 90℃), the mixer motor stops, the display shows communication loss, and the dashboard occasionally goes black.

Troubleshooting Process:
– Checked mixer motor mechanical structure: hand-turns freely, no seizing.
– Checked CAN bus terminal resistor: resistance normal, wiring intact.
– Checked PLC module supply voltage: stable at 24V.
– Measured relay output contacts at operating temperature: found contact resistance too high, causing voltage drop.

Root Cause: Relay contacts in the cab distribution box oxidize due to high temperature, leading to an open circuit in the control circuit.

Required Parts: Pumping control relay and wiring harness repair kit.