Carrier Delayed Ignition / Burner Flashback

Furnace makes loud banging or booming noise at startup when burners ignite.

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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, misaligned burners, low gas pressure, slow-opening gas valve

How to Fix / Troubleshooting

Safety first: Turn off power and gas. Delayed ignition can damage the heat exchanger and is a fire/explosion hazard.

  • Do not repeatedly restart: If you hear loud booms, shut the furnace down and do not continue to operate it.
  • Inspect burners (visual only): Remove the burner access panel and look for heavy rust, debris, or misaligned burners on the Carrier burner rack.
  • Check gas supply valves: Ensure the manual gas shutoff is fully open.

Cleaning and aligning burners and checking gas pressure should be done by a licensed HVAC technician. Do not attempt to adjust gas pressure yourself.

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Repair Difficulty

Professional Required 5/5

Required Part

Burner Assembly
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