Parktronic display problem

[clarkj0]

I have 1996 CL500 with parktronic.
The system works fine except that the white surround in the display above the right hand side air vent does not light when the system is on and the warning display itself - the two red and six yellow bars - is very dim.
Does anyone have any idea or experience why this might be or is it just old age?

Thanks,