Fault Phenomenon: Putzmeister M72 electrical circuits function normally when cold. After a thunderstorm (operating temperature), a short circuit occurs, fuses blow, and the machine eventually becomes inoperable.

Troubleshooting Process:
– Checked wiring harness protection: protection layer intact, no damage.
– Checked connector waterproofing: connector seals intact, no water ingress.
– Checked ground wires: connections secure, no corrosion.
– Measured wiring harness insulation resistance at operating temperature: found insulation resistance decreased.

Root Cause: The wiring harness insulation layer ages due to heat, causing an inter-phase short circuit.

Required Parts: Complete vehicle wiring harness assembly.