The volume increases without anythign showing on the display, you could be
drowning out the radio with the different road noises from the road surface.
Try driving along a tarmac road and testing it there; it should reduce the
road noise enough to let you hear the volume change. But remember the volume
doesn't change that much with speed i.e. from about 5 to 10 by going from 25
to 50 MPH by my ear I reckon it only goes up 2 maybe 3 points for every
doubling in speed. I usually stick it at 7 or 8 and raise it manually if I
am going over a concrete road surface.

Renault's system is better because you CAN set how fast the volume changes
not just wether or not it varies with road speed.

Chris

Life..... don't talk to me about life! my car still needs me to turn a key
to make it start.

I used to find the nest way to detect the auto-volume was to listen for
it reducing on decelleration, rather than the other way round.

Choose a nice empty motorway slip road and depress the cluth at the top
to reduce engine noise.  Then listen carefully as you brake to a halt
fairly quickly.

Nik