I assume you are seeing nothing at all on the display if so read on.
Citroen and Peugeot are one and the same French company. My Peugeot Partner Combi MPV is not disimilar to the Berlingo except I call it a flash Berlingo.
My owner book tells me how to replace ALL bulbs and there is no menton of a bulb in this multifuncional display unit, which is the same as the Berlingo as my daughter had a Berlingo and commented how much alike they are, its an electronic display unit fault.
You could check with Citroen web type in google search engine Citroen website.
Bob
February 2010