AL23
SDMO Glow Plug Circuit Failure

Controller displays AL23 indicating glow plug fault on diesel SDMO standby generator.

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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

Burnt-out glow plugs, Faulty glow plug relay, Loose or corroded glow plug busbar connections, Blown glow plug fuse

How to Fix / Troubleshooting

Safety first: Turn the generator OFF and disconnect the battery before working on the glow plug circuit.

  • Check glow plug fuse: Locate and test the fuse protecting the glow plug circuit. Replace with the correct rating if blown.
  • Inspect busbar and wiring: Ensure all nuts on the glow plug busbar are tight and free of corrosion. Repair any damaged wires from the SDMO controller/relay.
  • Test individual glow plugs: Remove the busbar and measure resistance from each glow plug terminal to ground. Replace any plug with open circuit or significantly different resistance.
  • Test glow plug relay: Command a preheat cycle from the controller and measure voltage at the glow plug busbar. If no voltage is present, replace the relay.
  • Reset AL23: After restoring proper operation, clear the alarm and verify improved cold starting.
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Repair Difficulty

Medium 3/5

Required Part

Glow Plug Relay
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