Many thanks for your suggestion. I investigated the heater, wich was OK with 26 Ohm and then the main board. Copper sheet of the relay printed board connection was burnt-out.
I made the surroundings of the relay pin and the relay pin itself clean. After that I made two new wired conductor (0,5mm) which I wired around the pin and carefully soldered to the rest of cooper sheet.
The malfunction was confusing. There was no heating at Eko program, where Intensive care was warm. But after several months the heater didn't work at all.
Thanks a lot. Maybe my experience can anybody use.
ivan
November 2011