Boiler shows E28, flue gas fan speed feedback fault (on modulating fans).

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

Faulty fan speed sensor, Broken tachometer wire, Defective modulating fan on Weishaupt boiler, Control board speed feedback circuit fault

Safety first: Isolate power before accessing the fan or control board.

Inspect tachometer wiring: Locate the low-voltage wires from the fan speed sensor to the control board. Check for damage or loose connectors.
Check fan connector: Ensure the multi-pin fan plug is fully seated.
Replace fan assembly: If the tachometer signal is missing or unstable and wiring is sound, the fan assembly (including sensor) may need replacement.

When to call a professional: Diagnosis of modulating fan systems and control boards should be done by a trained technician.

Hard 4/5

Modulating Fan Assembly

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