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Cummins/Onan — Generator Output Voltage Adjustment

A Cummins/Onan service procedure — check it applies to your exact model before use.

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Before you start

  • HAZARDOUS VOLTAGE! Touching uninsulated live parts inside the genset or connected equipment can result in severe personal injury or death.
  • Stand on a dry wooden platform or rubber insulating mat, make sure your clothing and shoes are dry, remove jewelry from your hands and use tools with insulated handles.

Procedure

  1. Disconnect all generator loads and connect accurate meters to measure AC volts and frequency.
  2. Start the genset and let voltage and frequency stabilize for 5 to 10 seconds.
  3. Rapidly press the control switch to START 6 times within 10 seconds to enter voltage set mode.
  4. To adjust voltage up, press the control switch to START and release quickly. Each time the switch is released, voltage will rise approximately 0.6 volt.
  5. To adjust voltage down, press the control switch to START and release in 1 second. Each time the switch is released, voltage will drop approximately 0.6 volt.
  6. Normal operation will resume in 20 seconds after the last adjustment. The last adjustment will be retained by the controller.

Tools required

  • accurate meters to measure AC volts and frequency

Specs & torque values

  • Voltage adjustment rate: approximately 0.6 volt per switch press release

Source: manual:981-0535 Onan HDKBA HDKBB Mobile Genset Service manual (10-2002).pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.