F7
Viessmann
Return temperature sensor fault
Return temperature sensor error, boiler may short-cycle or shut down
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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 return NTC sensor, Loose sensor contact on return pipe, Broken sensor wiring, Moisture ingress at connector
How to Fix / Troubleshooting
Safety: Turn off power and let the system cool.
- Locate return sensor: Find the return temperature sensor on the return pipe entering the Viessmann heat exchanger. Ensure it is properly clipped and insulated.
- Inspect cable and plug: Look for damage along the cable. Disconnect and reconnect the plug at the control board to clean the contacts.
- Check for condensation: On condensing models, inspect for condensate dripping onto the sensor or wiring. Correct any leaks and dry the area.
- Reset: Restore power and reset the fault. If F7 persists, the sensor likely needs replacement.
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Repair Difficulty
Medium
3/5
Required Part
Return Temperature Sensor (NTC)
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