E18
Weishaupt
Flue Gas Temperature Sensor Electrical Fault
Boiler shows E18, flue gas sensor fault or sensor short circuit.
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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
Shorted flue gas sensor, Damaged sensor cable, Incorrect wiring polarity (if required), Moisture ingress at sensor head
How to Fix / Troubleshooting
Safety first: Turn off power and allow the flue to cool before touching the sensor.
- Inspect sensor and cable: Check the sensor body for cracks and the cable for cuts or melted insulation. Replace if damaged.
- Check connections: Ensure the sensor is wired to the correct terminals and that screws are tight.
- Measure resistance: Disconnect the sensor and measure its resistance. A near-zero reading may indicate a short. Compare with Weishaupt specifications.
- Replace sensor: If readings are out of range, fit a new genuine Weishaupt flue gas sensor.
When to call a professional: If a new sensor does not resolve the fault, the control input may be defective.
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Repair Difficulty
Medium
3/5
Required Part
Flue Gas Temperature Sensor
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