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Solving Vaillant EcoTec "CON" Error?

Has anyone solved this issue? If so, what was the cause and solution?

Vaillant definition: no communication to mainboard connection error display mainboard.

No guesswork please, only those who have direct experience of this error.

Many thanks,

John

Jareus
March 2010

Vaillant Heating, Home Heating Systems

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?

Judith A
March 2010