Ideal · Independent+ Combi 24/30/35
L5
What L5 means
Return thermistor.
A boiler fault code alone is not a gas or carbon-monoxide emergency. If you smell gas, a CO alarm sounds, or someone has possible carbon-monoxide symptoms, leave and call 0800 111 999 from outside.
Safe check: Follow the user guide restart instruction once. Do not open the boiler or inspect wiring or sensors.
Gas Safe registered engineer: The fault remains or returns after the user guide action; contact Ideal if the boiler is under warranty or arrange a Gas Safe registered engineer.
Official source: Independent+ Combi User Guide · §8 Fault Codes, printed p. 8