LED 4 High

Ideal LED 4 Fault Code

Also written as LED4 — same fault.

The Ideal LED 4 fault code means: your boiler is signalling an electrical wiring issue or a faulty thermostat connection, which is preventing it from communicating correctly to start your heating or hot water.. It appears on 3 Ideal models in our database.

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.

Technical description: Application of power: Flash > 1/sec in sync with LED 3; Control 'stat open circuit or waiting for demand: On; Fan start up: Flash > 1/sec; Run: On; Pump over-run: Off; Lock-out: Off; Sensor Faults: Off; Reverse polarity: Flash > 1/sec alternately with LED 3.
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Ideal models that show the LED 4 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Ideal LED 4 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026