Fault Code 4155
Cummins Excitation System Overcurrent

Controller shows Fault Code 4155 – Generator Field Overcurrent / Excitation Fault

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Shorted rotor field winding, Faulty AVR driving excessive current, Shorted exciter diodes, Wiring short in excitation circuit

How to Fix / Troubleshooting

Safety first: Isolate generator from load and disable automatic start. Allow rotating parts to stop before opening generator end covers.

  • Visual inspection: Look for burnt wiring or insulation in the generator end and excitation circuit.
  • AVR check: Inspect AVR for signs of overheating or damage. Verify wiring against the Cummins schematic.
  • Rotor field test: Resistance and insulation tests on the rotor field should be performed by qualified personnel with appropriate instruments.
  • Service recommendation: Due to the complexity and risk, excitation overcurrent faults should be handled by a Cummins-authorized service center.
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Repair Difficulty

Professional Required 5/5

Required Part

Generator Rotor Field
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