AL15
FG Wilson
Generator Earth Fault Protection Trip
Controller displays AL15 – Earth Fault / Ground 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
Insulation breakdown in alternator windings, Damaged output cable insulation touching earth, Moisture ingress in junction boxes, Incorrect neutral-earth bonding
How to Fix / Troubleshooting
Safety first: Treat this as a serious electrical fault. Isolate the generator, open the output breaker, and lock out/tag out. Do not re-energize until the fault is located.
- Visual inspection: Inspect the alternator terminal box, cable glands, and output cables for signs of damage, burning, or moisture.
- Check junction boxes and ATS: Open downstream junction boxes and the ATS generator compartment to look for water ingress or cable insulation damage.
- Insulation resistance test: Using a megohmmeter (by a qualified electrician), test phase-to-earth and neutral-to-earth resistance. Low readings indicate insulation failure.
- Drying and cleaning: If moisture is present, dry the affected areas thoroughly and clean tracking paths. Re-test insulation before re-energizing.
- Professional repair: If alternator windings show low insulation resistance, the alternator may require rewinding or replacement by a specialist.
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Repair Difficulty
Professional Required
5/5
Required Part
Alternator Stator Windings
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