Vaillant ecoTEC plus Installation And Maintenance Instructions Manual page 30

Appendix
Code Meaning
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 start-
ing pump
F.76 Overheating protection on primary heat ex-
changer has responded
F.77 Fault: Flue non-return flap/condensate pump
F.83 Fault: Flow and/or return temperature sensor
temperature change
F.85 Fault: Flow and return temperature sensors
incorrectly installed
F.87 Ignition transformer not connected
F.88 Gas valve not connected
F.89 Incorrect pump detected
con No communication with the PCB
30
Cause
Interruption/short circuit of water pressure sensor, interruption/short
circuit to GND in supply line 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
Water pressure sensor and/or pump defective, air in the heating installa-
tion, insufficient water in the product; check adjustable bypass, connect
external expansion vessel to the return
Cable or cable connections for safety fuse in primary heat exchanger or
primary heat exchanger defective
No response from flue non-return flap or condensate pump defective
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
The flow and/or return temperature sensors have been installed on the
same pipe/incorrect pipe
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
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
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
Communication fault between display and PCB in the electronics box
Installation and maintenance instructions ecoTEC plus 0020200871_00