Fault Phenomenon: XCMG HB70K boom functions normally when cold. During large boom movements (operating temperature), the boom limit fails, causing it to exceed the limit position and eventually collide.

Troubleshooting Process:
– Checked boom limit switch: switch installed correctly, no looseness.
– Checked limit wiring: wiring intact, connections normal.
– Checked boom controller: controller logic normal, no errors.
– Measured limit switch signal at operating temperature: found signal constantly on or off.

Root Cause: The internal microswitch of the boom limit switch deforms due to heat, causing the contacts to fail.

Required Parts: Boom limit switch.