Immergas Fan Speed Control / Tachometer Fault

Display shows 28, boiler may not modulate correctly, unstable operation

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

Defective fan speed sensor, Damaged fan wiring, Faulty PWM control from PCB

Safety: Isolate power before accessing the fan or PCB.

Steps:

1. Listen for fan modulation: The fan should change speed as the boiler modulates. If it runs at one speed or surges, there may be a control issue.
2. Inspect fan connector: Ensure the multi-pin connector is fully seated and free of corrosion.
3. Technician tests: Check tachometer signal from the fan to the PCB with a meter or oscilloscope. Replace the fan if no signal. If the fan is good, replace the PCB.

Hard 4/5

Modulating Flue Fan

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