Vaillant ecoFIT sustain 615 Installation And Maintenance Instructions Manual page 34

Appendix
Fault code Meaning
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
F.89 Fault: Pump
Connection No communication between the PCB
and the user interface
34
Possible cause
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 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
Electronics defective
Installation and maintenance instructions ecoFIT sustain 0020277252_00