My recent purchase, e61 530d 2004, has a periodic clicking noise from below the steering wheel. I am quite sure it is a relay of some sort (at least I think so). It seems more frequent when I pass a bump in the road (however not always) but other than that there is no systematic pattern.

Any suggestion to what it could be?

 

Does the sound stop if you turn off the fan?

In my car there is a strange very vague sound, almost similiar to a relay clicking fast, when I turn in a round about. If I turn off the fan the sound stops so I guess it has something to do with the fan.

(My brother in law drives a saab 9-5 and a leaf found its way down to the fan, sounded like my sound although my sound is a lot weaker in volume. I fixed his problem by banging the panels around the fan area. Suddenly the leaf got loose and problem solved...
For me a very light object may be laying around my fan, perhaps making the sound when I turn. Perhaps same as yours?