E6
ATAG
Flow Temperature Sensor Fault
Furnace shows E6 and stops, often during hot water or heating demand
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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
Defective NTC flow sensor, Loose sensor wiring harness, Sensor not properly inserted into flow pipe pocket
How to Fix / Troubleshooting
Safety first: Isolate power and allow the unit to cool before handling sensors.
- Locate the flow temperature sensor (NTC) on the flow pipe leaving the primary heat exchanger.
- Check the electrical connector for corrosion or looseness. Unplug and reseat the connector.
- Ensure the sensor is fully inserted into its pocket or clamped securely to the pipe, with good thermal contact.
- Visually inspect the cable for damage or pinching.
- If you have a multimeter and the service manual, measure the sensor resistance at a known temperature and compare to the ATAG NTC chart. Replace the sensor if readings are out of range.
- Restore power and reset the boiler. If E6 persists, the control board input may be faulty and requires professional diagnosis.
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Repair Difficulty
Medium
3/5
Required Part
ATAG NTC flow temperature sensor
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