Fault Phenomenon: Zoomlion ZLJ5530THB first boom raises normally when cold. After reaching operating temperature (oil temp 85℃), the first boom raises slowly accompanied by a whining sound, eventually stopping.

Troubleshooting Process:
– Checked pilot pressure: pressure value meets standard, no fluctuation.
– Checked main pump suction port: no air ingress, good sealing.
– Checked swashplate angle sensor: output linear when cold.
– Measured swashplate angle sensor at operating temperature: found sensor output signal is non-linear.

Root Cause: The internal circuit board of the swashplate angle sensor is short-circuited due to moisture and heat.

Required Parts: Main pump swashplate angle sensor.