Dash lights fault

[Audisimon]

Hi all got a problem with me dash/display lights, basically they don't work.
The car in question is a 1997 A6 2.5Tdi and didn't notice a problem until it started getting dark then noticed the display was down so turned the dimmer switch but nothing happened.
Checked the fuse which was blown so changed it but didn't make any difference. The fuse did not blow after that.
Seems to be some sort of short or something because when I turn the lights on at night time the air con display dims slowly.😳😳