High
Reverse polarity on Ideal British Gas RD

Your boiler is failing to start because the electrical supply wires have been connected in the wrong order, preventing the system from safely powering up.

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

LED 3 flash > 1/sec alternately with LED 4, LED 4 flash > 1/sec alternately with LED 3

From this model's manual
Verified against the Ideal British Gas Rd installation & service 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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