BoilerFaultCodes DU
Displayed during diverter valve actuator replacement sequence
Ideal INSTINCT2 Fault codes & diagnostics
36 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Gas 2019-present
GC Numbers 47-349-6947-349-70
Download the Ideal INSTINCT2 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. 36 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 |
|---|---|---|
| 47-349-69 | INSTINCT2 30 | 2019–present |
| 47-349-70 | INSTINCT2 35 | 2019–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 INSTINCT2 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 36 documented codes
Tap any card for details
F[-]
Boiler has a fault for a specific error
F1
Low Water Pressure
F2
FLAME LOSS
F2 Or Fn Or Ln
Flame Loss
F3
Fan Fault
F4
FLOW THERMISTOR FAULT
F5
RETURN THERMISTOR FAULT
F6
Outside Sensor Fault
F7
Low Mains Voltage
Showing 11–20 of 36
F8
LOCKOUT DUE TO PARAMETER FAULT
F8 or L8
PCB UNCONFIGURED/FAULTY OR GAS VALVE SHORT CIRCUIT
F8/L8
Lockout Due To Parameter Fault
F9
Displayed after power cycle during PCB replacement
F9 or L9
REPLACE PCB
F9/L9
PCB Fault
FA
NEGATIVE DIFFERENTIAL FLOW OR RETURN THERMISTOR FAULT
FN
FLAME LOSS
FU
DIFF GREATER THAN 50°C CHECK ISOLATION VALVES ARE OPEN CHECK PUMP CHECK RAD VALVES OPEN CHECK SYSTEM BLOCKAGES
L[-]
Boiler is in lockout for a specific error
Showing 21–30 of 36
L1
Flow Temperature Overheat Lockout
L2
Ignition Lockout
L4
FLOW THERMISTOR FAULT
L4 Or F4
Flow Thermistor Fault
L5
RETURN THERMISTOR FAULT
L5 Or F5
Return Thermistor Fault
L6
False Flame Lockout
L8
LOCKOUT DUE TO PARAMETER FAULT
L9
PCB FAULT
LC
Ignition reset occurred 5 times within 15 minutes
Showing 31–36 of 36
LN
FLAME LOSS
oF
Displayed after pressing restart during PCB replacement
SH
Displayed during diverter valve actuator replacement sequence
SL
Displayed after viewing the last 3 faults during diverter valve actuator replacement
UF
Displayed during diverter valve actuator replacement sequence
uP
Displayed when turning power on during PCB replacement
Boiler cover options
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
Approved partner
Get a quote →
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Affiliate links. We may earn a commission at no extra cost to you.