Concord Flame Disturbance or Pressure Switch Opening on Blower Start

Furnace starts normally but shuts down 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

Cracked heat exchanger, Negative pressure in furnace room, Loose burner assembly, Faulty pressure switch or tubing

How to Fix / Troubleshooting

Safety: This symptom can indicate a cracked heat exchanger and potential carbon monoxide hazard. Turn off the furnace and do not operate until inspected.

Steps:

  • Check for LED codes: Note any pressure switch or flame loss codes when the blower starts.
  • Room pressure: Ensure the furnace room has adequate combustion air and that exhaust fans are not creating strong negative pressure.

Recommendation: Have a qualified HVAC technician perform a detailed heat exchanger inspection and combustion analysis.

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Repair Difficulty

Professional Required 5/5

Required Part

Heat Exchanger
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