My cluster warning lights on my '91 SL would flash and my gauges reset when I used the turn signal. I did some experimenting and concluded there was a problem with voltage regulation on the cluster circuit board. A friend who is a cicuit designer suggested that there may be a large electrolytic capacitor in the power supply that had dried-out. I took the cluster out, removed the back cover, removed the main board from within the back cover, and then examined the components. There was one large electolytic on the board, and sure enough, it was in the power supply circuit. The cap is rated 470uF, but when I removed it and measured its value with my meter, it read just .2nF It's value had diminished by more than 99%.

I replaced the bad cap with a new 470uF from Radio Shack. Part number is 272-1030. No more flashing or cluster reset when I use the turn signals now.