Help with my dads 92 Marquis Digital Dash

[FTLOSM]

Called my dad today to say happy birthday and he was telling me of a problem he is having with his digital dash. He has a 92 Marquis LS and it has the full digital dash, no problems till recently but as he drives (mostly expressway btw) his digital dash jumps around 58, 63, 56,64 etc, he said once in a while it actually even reads 0 when he is driving 55mph!

He said it didn't really bug him too much except he can't use the cruise control because it tries to adjust speed and is very erratic due to the digital dash issue.

He works at a steel mill and I know the cars have this weird steel dust build up, it actually ruins car finishes, I wonder if anyone has heard of something like this and if so what he can look at or replace, clean adjust (thinking maybe years of the steel mill have gunked up some sensor somewhere?).

Thanks for any help on this, I will pass any idea onto him

Bill

[Stevo2]

Could be a bad speed sensor or connection on the tranny. Maybe a bad connection or solder joint on the back of the dash cluster?