Miller Flame Disturbance or Grounding Issue

Furnace starts normally but shuts off when the blower comes on.

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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

Loose ground connection, Blower-induced negative pressure in burner area, Cracked heat exchanger, Poor combustion air supply

How to Fix / Troubleshooting

Safety: This symptom can indicate a cracked heat exchanger or unsafe combustion. Turn off gas and power and consider professional inspection.

  • Check ground connections: Tighten all ground screws on the control board, burner rack, and furnace chassis.
  • Inspect burner compartment seal: Ensure burner access panel and gaskets are intact to prevent blower air from disturbing the flame.
  • Verify combustion air: Make sure the furnace has adequate combustion air openings and that they are not blocked.
  • Professional heat exchanger check: Have a licensed technician inspect the heat exchanger for cracks or leaks and perform combustion analysis.
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Repair Difficulty

Professional Required 5/5

Required Part

Heat Exchanger
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