Controller displays “Undervoltage” or “Low Voltage” and either prevents transfer or shuts down the generator.

Safety first: Place generator in OFF and open the output breaker. Do not allow the transfer switch to connect loads while voltage is low.

Steps:

• Check engine speed: Start the generator in manual mode with no load (if possible) and listen for labored or slow engine speed. If the engine sounds slow, check fuel supply and air filter, and inspect the mechanical governor linkage for binding.
• Measure voltage: With a multimeter, measure output at the generator lugs. If voltage is low on all phases with normal engine speed, suspect the AVR or alternator excitation circuit.
• Inspect alternator wiring: With the unit off, check all stator and rotor connections for tightness and signs of overheating.
• Reduce load: If undervoltage occurs only when large loads start, stagger load startup or reduce total connected load to within the generator’s rated capacity.
• Replace AVR if needed: If wiring and engine speed are correct, replace the AVR with the Eaton-approved part and retest.