BoilerFaultCodes Application of power
Flash > 1/sec in sync with LED 4
Ideal RD2 Fault codes & diagnostics
8 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Regular Natural Gas 11-23 kW 2001 onwards Discontinued
GC Numbers 41-392-7241-392-7341-397-56
Replaced by: Classic
Download the Ideal RD2 manual
PDF
Versions & GC numbers
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 2 High
6 Unrated
Which version do you have?
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 41-392-72 | RD2 4100 | 2001–present |
| 41-392-73 | RD2 4125 | 2001–present |
| 41-397-56 | RD109 | 2003–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Ideal RD2 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 8 documented codes
Tap any card for details
Control 'stat open circuit or waiting for demand
On
Fan start up
Off
Lock-out
Flash < 1/second
Pump over-run
On
Reverse polarity Your boiler is failing to start because the electrical supply wires have been connected the wrong way around.
Your boiler is failing to start because the electrical supply wires have been connected the wrong way around.
Parts commonly replaced
- External electrical supply wiring
- Fused spur
Run
Off
Sensor Faults Your boiler has detected an issue with one of its internal heat sensors and has stopped working to ensure safety.
Your boiler has detected an issue with one of its internal heat sensors and has stopped working to ensure safety.
Parts commonly replaced
- NTC Sensor
- Wiring harness
Status & diagnostic codes 2 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
2 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
LED 3 Diagnostic Your boiler is currently experiencing a sensor error or electrical fault that is preventing it from operating correctly. LED 4 Diagnostic 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.