Fault Phenomenon: Co-Nele KNL5700 warning functions normally when cold. During nighttime operations (operating temperature), the warning light does not work, no audible alarm sounds, creating a safety hazard.

Troubleshooting Process:
– Checked bulb: bulb intact.
– Checked buzzer: buzzer normal.
– Checked switch: switch function normal.
– Measured warning circuit voltage at operating temperature: found voltage zero.

Root Cause: The warning light relay coil opens due to heat, causing an open circuit in the circuit.

Required Parts: Warning light relay and wiring harness.