Re: Dash backlighting
If you wire them like that, it means your sidelights are always on when the ignition is - which mine & yours aren't with the black dials.
The backlight illumination isn't part of the lighting circuit as such - it's part of the power to the instruments, which is then switched over to a sidelight function when you turn any of the lights on (i.e. it then gives you the little sidelight symbol in the rev counter, and the rheostat works).
I did a lot of diagnostics & fuse pulling with mine in the first day of ownership as the illumination and power to the instruments kept blowing a high-level fuse - it turned out to be a 2p piece behind the ashtray, shorting out that light connector.
Just Sold: 2001 156 2.4 JTD (140) Sportwagon Veloce
Replaced by: 2004 (54) Saab 9-5 2.2TiD Linear Sport
Also own: 2007 (07) Vauxhall Astra Twintop 1.6