High
36 on Ideal Logic Max Heat 2

Your boiler has lost the signal from the sensor that monitors the water temperature, meaning it cannot safely regulate its heat and has shut down to protect itself.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Flow thermistor open circuit

Shared across the Logic Max HEAT2 range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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.

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All 84 fault codes on the Logic Max Heat 2

Seeing a different code? Every code this model can display, in one place.

4.24.34.44.54.64.74.84.94.104.114.124.134.144.154.16059.1.59.1.81213141516171819242528293031323738435460657071758283113115116Blocked Flue/CondensateE4EAEdF9Fan FaultFdFlame LossFlame On Before Gas OnFlame on before gas valve onFlow Thermistor FaultFlow/Return ReversedFUSEGas Valve FaultH nH0Ignition LockoutL AL EL1LCDLow Mains VoltageNO CH OPERATIONNo Water FlowOutside Sensor FaultOverheat LockoutP1P4PCB FaultReturn ThermistorReturn Thermistor FaultRoom Thermostat FaultService DueService RequiredSpare PCB Not SetToo Many Restarts

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