Why am I getting a buzzing sound from behind the dash of my peugot partner?

I think a relay is on the way out as I get a loud buzz from behind the instrument panel. It could also explain the fact that I have no wipers, heater fan, indicators or panel lights until I have started the van and revved up the engine.
Also, now, the van won't start and it seems to be a diesel starvation problem

Andyman 250
January 2010