AL23
Kohler-SDMO Ground Fault Protection Trip

Controller shows AL23 / Earth Fault or Ground Fault Alarm

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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

Insulation failure in load cables, Moisture ingress in junction boxes, Incorrect neutral-earth bonding, Faulty earth fault relay or CT wiring

How to Fix / Troubleshooting

Safety first: Isolate generator and mains supplies. Only qualified electricians should work on ground fault issues.

  • Inspect cabling: Check generator output cables and load feeders for damage, water ingress, or burned insulation.
  • Test insulation: Use an insulation resistance tester (megger) to test phase-to-earth and neutral-to-earth resistance. Low values indicate a fault.
  • Check earth fault relay: Verify CT connections and settings on the earth fault relay or in the APM controller. Correct any wiring errors.
  • Dry and repair: Dry out any damp enclosures and replace damaged cables or terminations.
  • Reset alarm: After repairs, clear AL23 and test under supervision.

Ground faults can be dangerous and complex; involve a qualified technician for diagnosis and repair.

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Repair Difficulty

Professional Required 5/5

Required Part

Earth Fault Relay / CT Assembly
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