K1c bed problem

I am currently losing faith in my K1c, I keep getting the dreaded 2092 error, despite replacing the board, replacing the hot end etc. Creality fault code list says "ADC out of range, this usually occurs when heater temperature exceeds its configured minimum or maximum temperature. " It appears that the bed heats up immediately on suppling power to the printer, I also get a chamber heat warning, any ideas please ??