LED flashes code 34; furnace attempts ignition but burners do not light or light briefly then go out.
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power and gas before removing burner or ignition components. Avoid repeated ignition attempts if burners fail to stay lit.
Steps:
- Clean flame sensor: Remove the flame sensor rod and gently clean with fine steel wool until shiny. Reinstall so the rod is fully in the burner flame.
- Check ground connections: Verify that the burner assembly is securely fastened to the furnace chassis and that the green ground wire from the control board is tight on clean metal.
- Inspect burners: Remove burners if accessible and check for rust, debris, or misalignment that could cause uneven flame. Clean with a soft brush and compressed air.
- Inspect ignitor position: Ensure the hot surface ignitor is properly positioned so the gas stream crosses the glowing element. Adjust mounting if necessary.
When to call a technician: If flames light but drop out after a few seconds despite a clean sensor and good ground, gas pressure or control board flame sensing may be at fault and require professional testing.