F.020
The safety cut-out (SCO) interrupts the gas valve control. The gas valve was closed because the temperature of the flow or return temperature sensor has exceeded the maximum limit.
Vaillant ecoTEC Plus Combi
Possible cause
Insufficient/no water in the product.
Measure
1. Fill the heating installation.
2. Check the product and the system for leakages.
Possible cause
Fault in the electrical connection for the flow temperature sensor
Measure
Check and, if required, replace the wiring harness between the PCB and sensor, including all plug connections.
Possible cause
Fault in the electrical connection for the return temperature sensor
Measure
Check and, if required, replace the wiring harness between the PCB and sensor, including all plug connections.
Possible cause
Flow temperature sensor defective
Measure
Check and, if required, replace the flow temperature sensor.
Possible cause
Return temperature sensor defective
Measure
Check and, if required, replace the return temperature sensor.
Possible cause
The pump is defective.
Measure
Check and, if required, replace the pump.
Possible cause
3-port diverter valve defective or blocked
Measure
Check and, if required, replace the 3-port diverter valve.
Possible cause
Water pressure sensor defective
Measure
Check and, if required, replace the water pressure sensor.
Possible cause
Volume flow sensor defective
Measure
Check and, if required, replace the volume flow sensor.
Possible cause
Black discharge via the ignition cable, ignition plug or ignition electrode
Measure
Check the ignition cable, ignition plug and ignition electrode.
This code also applies to: