Starting prblems - Fiat Ducato Campervan - first generation

Hi,

We have an old campervan that is great fun, but this year wont start, there is power in the battery - the dash does not light up so there mest be an electrical fault that stops current getting to the starter motor.
Does any one know where to get hold of the electrical diagrams or Haynes manual? Or has any one had a similar problem?

John