AL17
Kohler-SDMO Mains Sensing / Auto Start Logic Fault

Controller shows AL17 / Mains Failure but generator does not start in AUTO

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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

Incorrect mains voltage sensing wiring to controller, Faulty mains sensing module, Disabled AUTO mode or incorrect start delay settings, ATS feedback contacts miswired

How to Fix / Troubleshooting

Safety first: De-energize control circuits where possible and follow lockout/tagout procedures. Work only if you are qualified for control wiring.

  • Check AUTO mode: Confirm the APM controller is set to AUTO and that no active alarms are preventing start.
  • Verify mains sensing: Measure mains voltage at the sensing terminals on the controller. Ensure correct phase and neutral connections and that voltage is within configured thresholds.
  • Inspect ATS feedback: Check the auxiliary contacts from the ATS that signal mains/generator availability to the controller. Repair any broken or miswired contacts.
  • Review start parameters: In the controller menu, verify start delay on mains failure and stop delay on mains return are set appropriately.
  • Simulate mains failure: With caution, open the mains breaker feeding the ATS and observe if the controller initiates a start sequence. If not, suspect controller or sensing module failure.

Complex ATS and controller interactions may require a Kohler-SDMO service technician to reconfigure and test.

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Repair Difficulty

Hard 4/5

Required Part

Mains Sensing Circuit / Module
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