F.49 displayed, boiler unresponsive or resets intermittently, low voltage error

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

Undersized or unstable mains supply, Short circuit on low-voltage circuit (eBUS, thermostat wiring), Faulty external controls, Internal PCB power supply fault

How to Fix / Troubleshooting

Safety: Electrical work should be done with power isolated and by competent persons.

Checks:

Confirm that the mains supply voltage is within specification using a multimeter.
Disconnect external low-voltage controls (room thermostat, eBUS controls) one by one to see if the fault clears.
Inspect thermostat and control wiring for shorts or damage.

Repair: Replace or repair any shorted external wiring or controls. If F.49 persists with all external connections removed, the PCB's internal power supply may be faulty and require replacement by a technician.

Repair Difficulty

Hard 4/5

Required Part

Main Control PCB

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