Fault Phenomenon: Caterpillar 793 mining truck turning the key, the starter motor does not respond, instrument lights not on.

Troubleshooting Process:
– Checked battery: battery pack low power or terminals oxidized/loose.
– Checked power switch: emergency disconnect switch not reset or poor contact.
– Checked fuse: main power fuse blown.
– Checked starter relay: relay coil burnt.

Root Cause: The main battery positive terminal is loose due to vibration and oxidized, causing excessive contact resistance and inability to carry starting current.

Required Parts: Clean and tighten battery terminals, charge or replace battery.