Fix Dishlex Global 500 Dishwasher?

Hi,
My Dishlex 500 had a fried motor which I just replaced. It has been out of action for a year. With new motor in and power on I get the OF error - indicating overfill or overflow. If I hold down start button during power on, I get normal status but after water starts input - only get about 20mls showing in tank - the OF error returns. Any advice? Many thanks...
Mark