Check the polarity of the mains supply. If the live and neutral are reversed this problem occurs.
Other wise you may have the same problem as i had . There is a faulty batch of components that was fitted at manufacture . Cannon never recalled them and I was duped into paying for a yearly plan (£170 ) to have it fixed). I do not know the name of the faulty unit but the repair engineer told me that the faulty ones are marked with an unfilled little square whereas the good ones have a filled in black square symbol on them. I had bought the cooker for a house I was renovating. It was only used for 2 months out of twelve but had gone over the one year warranty period. So basically i was charged for something that was dodgy on leaving the factory.
The insurance firm Cannon use were very unhelpful,please beware. Best thing don't buy a Cannon cooker
joe
October 2009