BoilerFaultCodesWhat the manual says
Manufacturer manualDifferent temperature between flow and return
What causes this fault?
This fault occurs when the boiler detects that water is leaving the unit much hotter than it is when it returns, suggesting the water is stuck or moving too slowly. The most common reasons are a failing internal pump that can't push the water around, or a blockage caused by a buildup of sludge and debris in the system or heat exchanger.
This issue often surfaces in autumn when the heating is turned back on after the summer, as the pump can seize or debris can settle during the months of inactivity.
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 41E: no call-out fees, no surprise bills.
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