BoilerFaultCodes Connection
No communication between the main PCB and the user interface Electronics defective
Vaillant ecoFIT sustain 830 Fault codes & diagnostics
43 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Gas 2016-present
GC Number 47-044-72
Download the Vaillant ecoFIT sustain 830 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. 43 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 |
|---|---|---|
| 47-044-72 | ecoFIT sustain 830 VUW 306/6-3 (H-GB) | 2016–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 830 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 43 documented codes
Tap any card for details
F.00
Fault: Flow temperature sensor
F.01
Fault: Return temperature sensor
F.10
Short circuit: Flow temperature sensor
F.11
Short circuit: Return temperature sensor
F.12 and F.91
Short circuit: Cylinder temperature sensor
F.13
Short circuit: Temperature sensor for the domestic hot water cylinder
F.20
Safety shutdown: Overheating temperature reached
F.22
Insufficient water pressure in the heating installation
F.23
Safety shutdown: Temperature spread too great (NTC1/NTC2)
Showing 11–20 of 43
F.24
Safety shutdown: Temperature rise too fast
F.25
Safety shutdown: Flue gas temperature too high
F.27
Safety shutdown: Fault in flame detection
F.28
Fault: Ignition unsuccessful when starting up
F.29
Fault: Flame loss
F.32
Fan frost protection function active: Fan speed outside the tolerance values
F.49
eBUS fault: Voltage too low
F.61
Fault: Gas valve assembly control
F.62
Fault: Gas valve switch-off control
F.63
Fault: EEPROM
Showing 21–30 of 43
F.64
Fault: Electronics/sensor/analogue-to-digital converter
F.65
Fault: Electronics temperature too high
F.67
Values sent back by ASIC is incorrect (flame signal)
F.68
Fault
F.70
Invalid product code (DSN) Display and PCB replaced at same time and Device Specific Number not reset, wrong or missing output coding resistor
F.71
Fault: Flow/return temperature sensor Flow temperature sensor signalling constant value: Flow temperature sensor incorrectly positioned on flow pipe, flow temperature sensor defective
F.72
Fault: Deviation in the water pressure sensor/return temperature sensor Flow/return NTC temperature difference too great → flow and/or return temperature sensor defective
F.73
Fault: Water pressure sensor not connected or has short-circuited Interruption/short circuit of water pressure sensor, interruption/short circuit to GND in supply pipe to water pressure sensor or water pressure sensor defective
F.74
Fault: Electrical problem in the water pressure sensor Line to water pressure sensor has a short circuit to 5V/24V or internal fault in the water pressure sensor
F.75
Fault: Pressure sensor Pressure switch defective
Showing 31–40 of 43
F.76
The safety cut-out in the primary heat exchanger is defective Safety cut-out feedback does not match the gas valve assembly feedback
F.77
Fault: Condensate or smoke No response, flue non-return flap defective
F.78
Interruption to DHW outlet sensor at external control UK link box is connected, but domestic hot water NTC not bridged
F.83
Fault: Dry fire When the burner starts, the temperature change registered at the flow or return temperature sensor is non-existent or too small: Insufficient water in the product, the flow or return temperature sensor is not in the correct position on the pipe
F.84
Fault: Flow/return temperature sensor Values not consistent, difference < -6K Flow and return temperature sensors signalling implausible values: Flow and return temperature sensors have been inverted, flow and return temperature sensors have not been correctly installed
F.85
Fault: Temperature sensor The flow and/or return temperature sensors have been installed on the same pipe/incorrect pipe Temperaturesensor not connected or is connected incorrectly
F.86
Fault: Underfloor heating contact Underfloor heating contact open, sensor disconnected or defective
F.87
Fault: Electrodes Electrodes not connected or they are connected incorrectly, short circuit in the cable harness
F.88
Fault: Gas valve assembly Gas valve assembly not connected or it is connected incorrectly, short circuit in the cable harness
F.89
Fault: Pump Pump not connected or it is connected incorrectly, incorrect pump connected, short circuit in the cable harness
Showing 41–43 of 43
F.97
Main PCB self-test failed Main PCB defective
S.04
Heating mode active
S.14
Hot water generation active
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