Vaillant ecoFIT sustain Series Installation And Maintenance Instructions Manual page 44

Fault code Meaning
F.67 Value sent back by ASIC is incorrect
(flame signal)
F.68 Fault: Unstable flame (analogue input)
F.70 Invalid product code (DSN)
F.71 Fault: Flow/return temperature sensor
F.72 Fault: Deviation in the water pressure
sensor/return temperature sensor
F.73 Fault: Water pressure sensor not con-
nected or has short-circuited
F.74 Fault: Electrical problem in the water
pressure sensor
F.75 Fault: Pressure sensor
F.76 The safety cut-out in the primary heat
exchanger is defective
F.77 Fault: Condensate or smoke
F.78 Interruption to DHW outlet sensor at
external control
F.83 Fault: Dry fire
F.84 Fault: Flow/return temperature sensor
F.85 Fault: Temperature sensor
F.86 Fault: Underfloor heating contact
F.87 Fault: Electrodes
F.88 Fault: Gas valve assembly
F.89 Fault: Pump
F.97 Main PCB self-test failed
Connection No communication between the main
PCB and the user interface
44
Possible cause
Implausible flame signal, electronics defective
Air in gas, gas flow pressure too low, incorrect air ratio, incorrect gas in-
jector, ionisation flow interruption (cable, electrode)
Display and PCB replaced at same time and Device Specific Number not
reset, wrong or missing output coding resistor
Flow temperature sensor signalling constant value: Flow temperature sensor
incorrectly positioned on flow pipe, flow temperature sensor defective
Flow/return NTC temperature difference too great → flow and/or return tem-
perature sensor defective
Interruption/short circuit of water pressure sensor, interruption/short circuit
to GND in supply pipe to water pressure sensor or water pressure sensor
defective
Line to water pressure sensor has a short circuit to 5 V/24 V or internal fault
in the water pressure sensor
Pressure switch defective
Safety cut-out feedback does not match the gas valve assembly feedback
No response, flue non-return flap defective
UK link box is connected, but domestic hot water NTC not bridged
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
Values not consistent, difference < -6 K
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
The flow and/or return temperature sensors have been installed on the same
pipe/incorrect pipe
Temperature sensor not connected or is connected incorrectly
Underfloor heating contact open, sensor disconnected or defective
Electrodes not connected or they are connected incorrectly, short circuit in
the cable harness
Gas valve assembly not connected or it is connected incorrectly, short circuit
in the cable harness
Pump not connected or it is connected incorrectly, incorrect pump connec-
ted, short circuit in the cable harness
Main PCB defective
Electronics defective
Installation and maintenance instructions ecoFIT sustain 0020230529_06