I've had this problem twice after power outage and both times I've fixed it by exposing the PCB and with the boiler switched on and asking for heat teasing the board with a hair dryer. Usually takes a few seconds and then the fan starts.
Ris
February 2021
Its most likely the PCB. other parts of faulty may vary from the heat exhanger or the pump.. but usually the pcb has to be changed to get rid of the CON problem :)
Ebin
September 2012
We have the same problem as you guys and have a flashing 'CON' error on our boiler. Can I please ask how much the replacement of the two PCB's cost?
Sarah
June 2010
this fault is the 2 boards are not comunicating.both boards need to be changed& the codes need to be set.this needs to be done by a vaillant engineer
bert
May 2010
Unfortunately not Judith.
The BG engineer called and replaced the two PCBs (main and display circuit boards). Possibly, a short circuit as he found a leak in the heat exchanger.
Regards,
John
Jareus
March 2010
Hi. No answer for you sorry but I do have the same problem. I'm phoning an engineer this morning but I wondered whether you had managed to resolve the issue yourself?