BoilerFaultCodesWhat the manual says
Manufacturer manualReturn sensor damaged or disconnected
What causes this fault?
This fault occurs when the boiler detects a conflicting temperature reading between its internal flow and return pipes. It usually happens because water isn't moving through the unit fast enough, or because one of the temperature sensors has become inaccurate or faulty. The boiler shuts down as a safety measure to prevent the heat exchanger from overheating due to this poor circulation.
This fault is more frequent in winter when heating systems are under high demand, as sludge or debris in the radiators can more easily restrict the water flow required for the boiler to operate safely.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Avoid the next call-out bill
A cover plan would handle faults like A42: no call-out fees, no surprise bills.
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