Fault Phenomenon: LiuGong HBT90 instrument readings are accurate when cold. At high cab temperatures (operating temperature), the instrument readings become distorted, the pointer swings erratically, and eventually goes black.

Troubleshooting Process:
– Checked sensor wiring: wiring intact.
– Checked instrument grounding: good grounding.
– Checked supply voltage: voltage stable.
– Measured internal temperature of the instrument at operating temperature: found temperature too high.

Root Cause: The crystal oscillator inside the instrument experiences frequency drift due to heat, leading to data processing errors.

Required Parts: Instrument display assembly.