So I was driving and my speedometer stopped working, then s**t started shutting off...okay, its my alternator...then i changed it out and the car started right up. I get in to drive it, and i take off and the speedometer is TWEAKING out..its going from like 5mph to 40 to 35, just all over the place....so Anyone have any idea what that might be from? And another this is that since i changed the alternator, when the car is warm is revs from like 1000 to 1700 up and down constantly....any help would be great! Oh and before the alternator died everything was fine.