BoilerFaultCodes 16
Ignition Lockout
Ideal Evomax Fault codes & diagnostics
34 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Gas 2001-present
GC Numbers 41-750-4241-750-4141-750-4041-750-3541-750-3441-750-33
Download the Ideal Evomax 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. 34 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 |
|---|---|---|
| 41-750-42 | Evomax 60P | 2011–present |
| 41-750-41 | Evomax 40P | 2011–present |
| 41-750-40 | Evomax 30P | 2011–present |
| 41-750-35 | Evomax 60 | 2001–present |
| 41-750-34 | Evomax 40 | 2011–present |
| 41-750-33 | Evomax 30 | 2011–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 Evomax faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 34 documented codes
Tap any card for details
76
FALSE FLAME LOCKOUT / ERROR 20
77
LOW WATER PRESSURE
78
FLAME LOSS
79
FAN FAULT
80
FLOW THERMISTOR FAULT
81
RETURN THERMISTOR FAULT
82
OUTSIDE SENSOR FAULT
83
FLOW/RETURN REVERSED
84
CYLINDER THERMISTOR FAULT
Showing 11–20 of 34
85
EXTERNAL INTERLOCK OFF
86
BCC FAULT
87
no CH but DHW ok
88
no DHW but CH ok
89
no DISPLAY
90
0-10V INTERFACE
BCC Fault
BCC missing or incorrect
Cylinder Thermistor Fault
DHW cylinder thermistor fault
Error 20
False Flame Lockout
Ext’ Interlock Off
External interlock circuit open
Showing 21–30 of 34
False Flame Lockout
Flame detected when not expected
Fan Fault
Fan operation fault
Flame Loss
Loss of flame during operation
Flow Thermistor Fault
Flow thermistor fault
Flow/Return Reversed
Flow and return pipework identified as reversed
Ignition Lockout
Boiler ignition lockout
Ignition Lockout [16]
Ignition Lockout
Low Mains Voltage
Mains voltage less than 160V
Low Water Pressure
System water pressure low
Outside Sensor Fault
Outside sensor fault
Showing 31–34 of 34
Overheat Lockout
Boiler system overheat lockout
PCB Fault
Main PCB fault or BCC missing
Return Thmr Fault
Return thermistor fault
Too Many Resets
5 resets within 15 mins
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