Hello. I have a 1990 Buick Riviera with some dash problems.

First, my dash lights no longer dim, or even com one. The instrument cluster will come on but all of the backlighting for the HVAC, radio, and gearshift don't come on. The instrument panel will no longer dim with the dimmer switch under the headlight switch. I have been told by the dealer that this is a very expersve fix. What is wrong and how can I fix this?

Second, my instrument cluster will occasionally blank out or read "error." If I shut the car off and restart it displays okay, but this is happening more and more frequently. I understand that this is a problem with the internal electronics of the cluster itself. Does anyone know how to trepair it or if there issomewhere that can repair it?

Any chance that rebuilding the instrument cluster will get my dash lights working again?

Thanks.

I would check 1 or all of the following;
There is a twilight sesor bulb in the center of your dash. That bulb may need replacement, as it senses darkness which turns on the backlights.
The dimmer part of your light switch may be corroded and need to be cleaned or replaced.
Your instrument cluster is going bad or your connection is also corroded and needs to be cleaned.
The dash panel is held in place by 4 torx screws. Two in the instrument cluster area underneath the top edge. And one each of the air vents on either side of the cluster.
Removal is fairly simple but go slowly as the rest of the dash panel is held in by clips. Be sure to grab the plastic dash panel by the part immediatly against the cluster so you don't pull off and ruin the top part of the trim panel.
Getting to the twilight bulb is far trickier. The vent plastic piece has to be removed. I have noticed that Buick went to a screwed in unit rather then a "snap in" style. If you have the former remove the 3 torx screws. If the latter, pry out carefully. Then you have to pry up the large dash panel. It is held in by snap clips starting from the outside in at about 6" intervals. Prying up is not advised as you run the risk of cracking the large part of the dash panel. I woul advise taking a flat piece of steel and put a 1/8" lip on it. Slid that in the groove and pull straight up.
The bulb is available at GM or believe it or not at Home Depot according to others on the Reatta forum.
The instrument cluster I have and would be happy to sell you if you are interested. Please PM me.
The problem you are dealing with is common to us Reattaites as the '88-91 Reatta is a nothing more then an improved '87-93 Riv. [lol]