AL17
FG Wilson Mains Sensing or ATS Communication Fault

Controller displays AL17 – Mains Failure Not Detected / ATS Fault (on integrated systems)

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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

Loss of mains voltage sensing to controller, Blown fuses in sensing circuit, Faulty ATS auxiliary contacts, Broken communication cable between ATS and generator controller

How to Fix / Troubleshooting

Safety first: Work only on de-energized control circuits. If mains is present, extreme caution is required; this work is best done by a qualified electrician.

  • Check mains sensing fuses: In the control panel or ATS, locate the small fuses protecting the voltage sensing lines to the controller. Replace if blown.
  • Verify sensing voltage: With a meter, confirm that the correct mains voltage is present at the controller sensing terminals.
  • Inspect ATS auxiliary contacts: Ensure that the feedback contacts indicating ATS position are operating and wired correctly to the controller.
  • Check communication cable: For systems using Modbus or proprietary links between ATS and generator, inspect the cable and connectors for damage.
  • Controller configuration: Confirm that the controller is configured for the correct mains voltage and sensing method (3-phase/1-phase).
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Repair Difficulty

Hard 4/5

Required Part

Mains Sensing Circuit
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