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Vaillant ecoFIT sustain 418 Fault codes & diagnostics
36 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
System Gas 2018-present
GC Number 41-694-34
Download the Vaillant ecoFIT sustain 418 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 |
|---|---|---|
| 41-694-34 | ecoFIT sustain 418 VU 186/6-3 OV (H-GB) | 2018–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 Vaillant ecoFIT sustain 418 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.00
Flow temperaturesensor interruption
F.01
Return temperaturesensor interruption
F.10
Flow temperaturesensor short circuit
F.11
Return temperaturesensor short circuit
F.13
Warm start sensor/cylinder temperaturesensor short circuit
F.22
Safety shutdown: Water deficiency
F.23
Safety shutdown: Temperature spread too great
F.24
Safety shutdown: Temperature rise too fast
F.25
Safety shutdown: Flue gas temperature too high
Showing 11–20 of 36
F.27
Safety shutdown: Flame simulation
F.28
Failure during start-up: Ignition unsuccessful
F.29
Failure during operation: Re-ignition unsuccessful
F.32
Fan fault
F.49
Fault: eBUS
F.61
Fault: Gas valve assembly actuation
F.62
Fault: Gas valve assembly switch-off delay
F.63
Fault: EEPROM
F.64
Fault: Electronics/NTC
F.65
Fault: Electronics temp.
Showing 21–30 of 36
F.67
Fault: Electronics/flame
F.68
Fault: Unstable flame signal
F.70
Invalid device specific number (DSN)
F.71
Fault: Flow temperature sensor
F.72
Flow and/or return temperature sensor fault
F.73
Water pressure sensor signal in the wrong range (too low)
F.74
Water pressure sensor signal outside correct range (too high)
F.75
Fault:Nopressurechangedetectionwhenstartingpump
F.76
Overheatingprotectiononprimaryheatexchangerhasresponded
F.77
Fault:Fluenon-returnflap/condensatepump
Showing 31–36 of 36
F.83
Fault:Flowand/orreturntemperaturesensor temperaturechange
F.85
Fault:Flowandreturntemperaturesensors incorrectlyinstalled
F.87
Ignitiontransformernotconnected
F.88
Gasvalvenotconnected
F.89
Incorrectpumpdetected
F.97
Fault:MainPCBself-testfailed
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