F.012
The domestic hot water connection temperature sensor has short-circuited.
Vaillant ecoTEC Plus Combi
Possible cause
Fault in the electrical connection for the domestic hot water temperature sensor
Measure
Check and, if required, replace the wiring harness between the PCB and sensor, including all plug connections.
Possible cause
Domestic hot water temperature sensor defective
Measure
Check and, if required, replace the domestic hot water temperature sensor.