Controller shows E13 and the generator shuts down unexpectedly during normal operation.

Safety first: Confirm the generator is OFF and cannot auto-start.

• Check emergency stop button: Locate the red E-STOP button on the Firman generator enclosure. If it is pressed in, twist or pull it to reset according to the label.
• Inspect E-STOP switch: Remove the switch from the panel and test continuity with a multimeter. Replace if it does not change state when actuated.
• Check remote stop wiring: If your system uses remote shutdown contacts (e.g., from a building management system), inspect the low-voltage wiring for shorts to ground or cross-connections.
• Verify controller inputs: At the control board, confirm that the emergency stop input terminals are not permanently grounded or bridged.

After resolving the cause, clear E13 on the controller and test run. If the fault recurs, the control board input circuit may be defective.