Fault Phenomenon: Caterpillar AP655D paver fan runs continuously or not at all, water temperature control fails.

Troubleshooting Process:
– Checked switch: temperature switch contacts stuck or open.
– Checked wiring: wiring shorted or open.
– Checked fan: fan motor normal.
– Checked water temperature: actual water temperature normal.

Root Cause: The engine coolant temperature switch failed, preventing the fan from automatically starting/stopping based on water temperature.

Required Parts: Replace engine temperature switch.