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Vaillant ecoFIT sustain 615 Fault codes & diagnostics
87 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
System Gas 2018-present
GC Number 41-694-30
Download the Vaillant ecoFIT sustain 615 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. 87 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 |
|---|---|---|
| 41-694-30 | ecoFIT sustain 615 VU 156/6-3 (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 615 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 87 documented codes
Tap any card for details
F.00
Fault:Flowtemperaturesensor
F.01
Fault:Returntemperaturesensor
F.10
Shortcircuit:Flowtemperaturesensor
F.11
Shortcircuit:Returntemperaturesensor
F.12
Shortcircuit:Cylindertemperature sensor
F.13
Shortcircuit:Temperaturesensorforthe domestichotwatercylinder
F.20
Safetyshutdown:Overheatingtemperat- urereached
F.22
Insufficient water pressure
F.23
Safetyshutdown:Temperaturespread toogreat(NTC1/NTC2)
Showing 11–20 of 87
F.24
Safetyshutdown:Temperaturerisetoo fast
F.25
Safetyshutdown:Fluegastemperature toohigh
F.27
Safetyshutdown:Faultinflamedetec- tion
F.28
Fault:Ignitionunsuccessfulwhenstarting up
F.29
Fault:Flameloss
F.32
Fanfrostprotectionfunctionactive:Fan speedoutsidethetolerancevalues
F.49
eBUSfault:Voltagetoolow
F.61
Fault:Gasvalveassemblycontrol
F.62
Fault:Gasvalveswitch-offcontrol
F.63
Fault:EEPROM
Showing 21–30 of 87
F.64
Fault:Electronics/sensor/analogue-to- digitalconverter
F.65
Fault:Electronicstemperaturetoohigh
F.67
ValuesentbackbyASICisincorrect (flamesignal)
F.68
Fault:Unstableflame(analogueinput)
F.70
Invalidproductcode(DSN)
F.71
Fault:Flow/returntemperaturesensor
F.72
Fault:Deviationinthewaterpressure sensor/returntemperaturesensor
F.73
Fault:Waterpressuresensornotcon- nectedorhasshort-circuited
F.74
Fault:Electricalprobleminthewater pressuresensor
F.75
Fault:Pressuresensor
Showing 31–40 of 87
F.76
Thesafetycut-outintheprimaryheat exchangerisdefective
F.77
Fault:Condensateorsmoke
F.78
InterruptiontoDHWoutletsensorat externalcontrol
F.83
Fault:Dryfire
F.84
Fault:Flow/returntemperaturesensor
F.85
Fault:Temperaturesensor
F.86
Fault:Underfloorheatingcontact
F.87
Fault:Electrodes
F.88
Fault:Gasvalveassembly
F.89
Fault:Pump
Showing 41–50 of 87
F.91
Shortcircuit:Cylindertemperature sensor
F.97
MainPCBself-testfailed
S.0
Heating mode: No requirement
S.01
Heating mode: Fan prerun
S.02
Heating mode: Pump prerun
S.03
Heating mode: Burner ignition
S.04
Heating mode: Burner on
S.05
Heating mode: Pump/fan overrun
S.06
Heating mode: Fan overrun
S.07
Heating mode: Pump overrun
Showing 51–60 of 87
S.08
Heating mode: Temporary shutdown after heating procedure
S.10
Domestic hot water mode: Requirement
S.11
Domestic hot water mode: Fan prerun
S.13
Domestic hot water mode: Burner ignition
S.14
DHW mode: Burner on
S.15
DHW mode: Pump/fan overrun
S.16
DHW mode: Fan overrun
S.17
DHW mode: Pump overrun
S.20
Domestic hot water mode: Requirement
S.21
Domestic hot water mode: Fan prerun
Showing 61–70 of 87
S.22
Domestic hot water mode: Pump prerun
S.23
Domestic hot water mode: Burner ignition
S.24
DHW mode: Burner on
S.25
DHW mode: Pump/fan overrun
S.26
DHW mode: Fan overrun
S.27
DHW mode: Pump overrun
S.28
Domestic hot water mode: Temporary shutdown of the burner
S.30
Room thermostat is blocking heating mode.
S.31
No heating demand: Summer mode, eBUS control, waiting period
S.32
Fan waiting time: Fan speed outside of the tolerance values
Showing 71–80 of 87
S.33
Forced fan operation until the pressure monitor is switched
S.34
Frost protection active
S.39
Underfloor heating contact open
S.41
Water pressure too high
S.42
Flue non-return flap closed
S.46
Frost protection mode (Comfort): Minimum load
S.53
Product in waiting period/operating block function due to water deficiency (flow/return spread too large)
S.54
Waiting period: Water deficiency in the circuit (flow/return spread too large)
S.76
Maintenance message: Check the water pressure
S.88
Product purging active
Showing 81–87 of 87
S.91
Maintenance: Demo mode
S.96
Automatic test programme: Return temperature sensor, heating demands blocked.
S.97
Automatic test programme: Water pressure sensor, heating demands blocked.
S.98
Automatictestprogramme:Returntemperaturesensor,heatingdemandsblocked.
S.99
Internalautomatictestprogrammes
S.108
Purgingthecombustionchamber,faninoperation
S.109
Product'sstandbymodeactivated
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