Today I was on my way back from school, stopped in traffic, and looked at my tach and it was jumpy so I looked at my voltometer and it was fine. But I gave it a little gas and it would stay jumpy the whole time. The voltometer was reading between the O and R. And my radio would always go off before the tach got jumpy and it stayed on the whole time. I took my U/D pullies off so thats not the problem. I noticed it would do it when I was stopped and pressed the brake. Then when I let off it would go back to normal.