Generator shuts down; controller displays AL13 – Generator Undervoltage

Safety first: Open the generator output breaker to protect loads. Stop the generator and isolate battery negative before opening terminal boxes.

• Visual inspection: Check alternator terminal box for loose or burnt connections. Tighten all power and sensing terminals.
• Check AVR fuses: Some AVRs have inline fuses; inspect and replace if blown, but investigate the cause of failure.
• Test no-load voltage: Start the generator with the breaker open and measure voltage. If near zero or very low, excitation may be lost (AVR or rotor issue).
• Reduce load: If undervoltage occurs only under heavy load, verify that total load is within the generator rating. Shed non-critical loads and retest.
• Replace AVR or consult specialist: If excitation is absent and wiring is intact, the AVR or alternator windings may be faulty; replacement or professional repair is required.