High
Return Thermistor Fault on Ideal Logic Max Heat 2

Your boiler has detected an issue with a temperature sensor that monitors the water returning from your radiators, preventing the system from heating up safely.

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

Wiring or resistance issues with the Return Thermistor located in the pump housing (upper LHS of boiler).

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.

What causes this fault?

This fault occurs when the boiler's control board receives an incorrect or missing signal from the sensor that measures the temperature of the water coming back from your radiators. The most common reason is that the internal sensor has developed a physical defect or the electrical connection has become loose or corroded over time.

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.

4.24.34.44.54.64.74.84.94.104.114.124.134.144.154.16059.1.59.1.8121314151617181924252829303132363738435460657071758283113115116Blocked 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 ThermistorRoom Thermostat FaultService DueService RequiredSpare PCB Not SetToo Many Restarts

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