Ducato headlights

Hi everyone, Just bought a 2005 fiat ducato motorhome 2800JTD and the dash lights have stopped working and also the dipped beam, all other lights ok. It does have an after market stereo, would this effect anything although I have disconnected this, checked the obvious fuses, light switch and all ok. Does anyone know if there is a dim dip relay on these and where it is, would be grateful for any help,
cheers Minta.

This sounds like it might be a problem with what the manual calls "dashboard earth". Unfortunately, I can't get my electronic manual to display diagrams to say where it is exactly. Hopefully someone else can help out here.
I know my manual problem is because it needs earlier versions of Internet Explorer to run correctly but my IE5 which I normally use for this freezes on loading.