Furnace indicates sensor plausibility error (e.g., flow and return temperatures inconsistent)

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

One or more NTC sensors out of calibration, Crossed sensor wiring on Hoval manifold, Poor thermal contact of strap-on sensors, Control board input fault

How to Fix / Troubleshooting

Safety: Isolate power before working on sensors.

Compare readings: In the service menu, compare flow, return, and DHW temperatures. Look for obviously incorrect values.
Check sensor mounting: Ensure strap-on sensors are firmly attached and insulated; immersion sensors must be fully inserted.
Verify wiring: Confirm each sensor is connected to the correct terminal pair on the Hoval controller.
Reset and monitor: After corrections, clear the error and monitor operation. Persistent plausibility errors may require sensor replacement or board diagnostics.

Repair Difficulty

Medium 3/5

Required Part

Temperature Sensors (NTC Set)

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