E09
Slant/Fin Flame Signal Weak or Intermittent

Boiler shows E09, burner shuts down, may coincide with high flue temperature or poor combustion

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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

Dirty burner assembly, Poor grounding of boiler chassis, Weak flame sensor signal, Incorrect gas/air mixture on Slant/Fin burner

How to Fix / Troubleshooting

Safety: Turn off gas and power. Allow boiler to cool before opening combustion chamber.

Steps:

  • 1. Clean flame sensor: Remove and gently clean the flame rod with fine abrasive pad. Reinstall ensuring it is fully in the flame.
  • 2. Inspect burner: Remove burner assembly if accessible. Brush off rust and debris from burner ports. Vacuum loose material. Do not alter port size.
  • 3. Check ground connection: Verify the green ground wire from the power supply is securely attached to the boiler chassis. Tighten any loose screws.
  • 4. Visual flame check: On restart, observe flame color through sight glass. A proper flame should be mostly blue with minimal yellow tips. Excessive yellow indicates poor combustion and requires professional adjustment.

Call a technician: If E09 recurs, a pro should measure flame rectification current, adjust gas pressure, and verify combustion with an analyzer.

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Repair Difficulty

Hard 4/5

Required Part

Flame Sensor
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