Safety first: Keep the generator output breaker open and verify with a meter that no voltage is present before touching terminals.

Confirm zero voltage: Measure line-to-line voltage at the alternator terminals with the engine running. If zero or very low, proceed with excitation checks.
Inspect AVR and fuses: Check the AVR for visible damage and test any associated fuses. Replace blown fuses with correct ratings and retest.
Check field circuit continuity: With the engine off and battery disconnected, measure resistance of the rotor field winding via the slip rings or field leads. An open circuit indicates a failed rotor requiring replacement or rewinding.
Restore residual magnetism (technician): In some cases, flashing the field with a DC source can restore magnetism. This should be done only by a qualified technician following Siemens procedures.
Replace AVR if needed: If field winding is intact but no excitation voltage is present, replace the AVR.

Generator runs but does not produce any AC output voltage.

Possible Causes