1999 Subaru Legacy SUS speedo problem?

So I just got a car that was as is. It is a 1999 Subaru Legacy SUS LTD. There is a problem with the speedo and odometer and trip. Every now and again it will work and somtimes it will just cut out even if i don't do anything. Now my question is could this be a bad sensor or could this be a bad cluster or wiring problem? I don't think it would be a sensor cause it would just go completely right? The part if it is the speedo since there were two for my year is one is 89 bucks the other one is 250 with out labor which would add to 500 and that might not even be the problem. I guess i'm just asking what yours thoughts may be and maybe this has happened on other subarus.