BoilerFaultCodes con
No communication with the PCB. Communication fault between the display and the PCB in the electronics box
Vaillant ecoFIT sustain 430 Fault codes & diagnostics
36 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
System Gas 2018-present
GC Number 41-694-35
Download the Vaillant ecoFIT sustain 430 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 |
|---|---|---|
| 41-694-35 | ecoFIT sustain 430 VU 306/6-3 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 430 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 temperaturesensor
F.72
Flow and/or return temperaturesensor 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: No pressure change detection when starting pump. Water pressure sensor and/or pump defective, air in the heating installation, insufficient water in the product; check adjustable bypass, connect external expansion vessel to the return
F.76
Overheating protection on primary heat exchanger has responded. Cable or cable connections for safety fuse in primary heat exchanger or primary heat exchanger defective
F.77
Fault: Flue non-return flap/condensate pump. No response from flue non-return flap or condensate pump defective
Showing 31–36 of 36
F.83
Fault: Flow and/or return temperature sensor temperature change. When the burner starts, the temperature change registered at the flow and/or return temperature sensor is non-existent or too small. Insufficient water in product, Flow or return temperature sensor not in correct position at pipe
F.85
Fault: Flow and return temperature sensors incorrectly installed. The flow and/or return temperature sensors have been installed on the same pipe/incorrect pipe
F.87
Ignition transformer not connected. Ignition transformer plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, electronics defective
F.88
Gas valve not connected. Gas valve plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, electronics defective
F.89
Incorrect pump detected. Unsuitable pump connected, PWM plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, electronics defective
F.97
Fault: Main PCB self-test failed. Main PCB defective
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