E09
Viadrus
Flue Gas Temperature Sensor Fault / Overtemperature
Furnace shows E09, burner stops, and the flue gas temperature is abnormally high.
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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
Blocked flue or chimney on Viadrus furnace, Failed flue gas NTC sensor, Loose flue sensor connection, Incorrect burner adjustment causing high flue temperature
How to Fix / Troubleshooting
Safety: Switch off power and gas. Do not operate the furnace with a suspected flue blockage due to carbon monoxide risk.
- Inspect chimney/flue: For Viadrus atmospheric or pressure‑jet oil/gas furnaces, have the chimney or flue inspected and swept by a qualified chimney professional. Look for soot buildup, collapsed liners, or bird nests.
- Check flue gas sensor: Locate the flue gas NTC sensor mounted in the flue hood or flue pipe. Inspect the cable and connector for heat damage. Reseat the connector.
- Measure sensor resistance: With power off, disconnect the sensor and measure resistance. Compare to the Viadrus NTC chart. Replace if out of range.
- Burner tuning: A combustion specialist should check burner settings (gas pressure, air shutter, oil nozzle size) to ensure flue gas temperature and CO/CO₂ levels are within Viadrus specifications.
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Repair Difficulty
Hard
4/5
Required Part
Flue Gas NTC Sensor
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