AL11
Kohler-SDMO Engine Preheater / Glow Plug Circuit Fault

Controller displays AL11 / Preheating Fault and the engine is hard to start in cold weather.

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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

Failed engine block heater or coolant heater, Blown preheat fuse, Faulty preheat relay, Broken wiring to glow plugs or heater element.

How to Fix / Troubleshooting

Safety first: Turn the controller to OFF, disconnect the battery negative terminal, and isolate the AC supply to any 230/400 V block heaters before inspection.

  • Check preheat indicator: On the APM controller, observe if the preheat icon or status appears before cranking. If not, suspect control or power issues.
  • Inspect fuses and relays: In the control panel, locate the preheat fuse and relay. Test the fuse with a multimeter and replace if open. Listen or feel for relay operation during the preheat command.
  • Measure heater resistance: Disconnect the block heater or glow plug harness and measure its resistance. An open circuit indicates a failed element.
  • Check AC supply (for block heater): Verify that the block heater supply breaker is ON and that the correct voltage is present at the heater terminals.
  • Reset alarm: After repairs, reconnect the battery, clear AL11, and test preheat operation by initiating a start sequence.

In very cold climates, ensure the heater is sized and powered correctly as per Kohler-SDMO recommendations.

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Repair Difficulty

Medium 3/5

Required Part

Engine Block Heater / Preheater
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