BoilerFaultCodesWhat the manual says
Manufacturer manualAutomatic Lockout. Thermistor reading outside of limits or difference between flow and casting thermistor readings is outside of limits.
What causes this fault?
This fault occur when the sensor responsible for monitoring the temperature of the boiler's main heat exchanger sends an incorrect or out-of-range signal to the control board. The most common cause is a physical failure of the thermistor itself due to age, or potentially a loose connection in the wiring that prevents the boiler from safely monitoring internal heat levels.
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 Casting Thermistor Fault: no call-out fees, no surprise bills.
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