when did you see all this work well., last week, month ,year,decade?
1990 is old car and also vastly more simple than todays cares with cluster on a CAN_BUS network
but will read the SM to you on this car. try
the problem is manuals are so rare on cars that old
there are 10 lamps in the cluster warning, are all 10 dead
AC/heat blower dead?, is a fuse or controls or motor dead. and not related to cluster.
digital does what.? odometer?
id say if all gauges there are dead, that power to the gauges
is dead,or the related grounds 18PIN CONNECTOR REAR.
AND UP TOP 1MORE CONNECTOR THAT MUST BE CONNECTED
IT HAS NO SPEEDO CABLE SO IS DIGITAL.
THE ODOMETER IS MECHANICAL COUNTER BUT IS ELECRTICALLY DRIVEN
THE ONLINE SERVICE manual shows no full sets of schematics
that is because no digital PDF documents then, so are crude limited scans,
so to fix any 1990 (90s) and older
buy the paper book used,
ebay is best,
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2553941.m570.l1313&_nkw=Cadillac+DeVille+1990+manual&_sacat=0
RED book
to fix a car this old needs a book, here they are.
even some on CD, hard to believe 500 pages scanned, buy them.