Ok so yesterday I was on a trip downstate in my 2003 jetta 2.slow, and on the interstate I was cruising around 70mph on cruise control when all of the sudden my car started to accelerate quickly and then decelerate and repeat, so I shut off the cruise control and was just cruising on my own when I looked down at the speedometer and it was just hovering around 70mph waving back and forth and not showing my actual speed. When I slowed down to around 60mph the speedometer would go back to working just fine but any time I hit more then 70mph it goes right back to not working correctly and waving back and forth. I'm thinking the problem with the speedometer is the same problem that is affecting my cruise control making it accelerate very quickly and decelerate quickly. Also no other instruments on my cluster have had any problems but the speedometer.
Has anyone else had this problem, or know what could be causing it? thanks in advance.