OPTIMAX HE 31C PROBLEM?

hi everyone i need to pick your brains i have an OPTIMAX HE 31c and the pressure is ok AT 1.5mb, it is an auto pilot combination boiler, now every time i put the plug on for the boiler the boiler seems to want to come on straight away and it sounds like a motor jamming close to the curcit board and and the motor jamms before the gas kicks in, it says noCN on the boiler and what does this mean as i the plumber did not give the person the manual to keep (stupid) HELP does enyone know the fualt for this please reply asap

Thank You
A Ford