Interesting Tach Issue

On my long list of things to do, has always been to get the tach working. Today I was doing some work, and noticed an ever so slight twitch of the tach needle. I first thought I had just imagined it. The previous owner told me the tach didn't work, so I have been under that impression for 6 years now. I dropped it and kept doing what I was doing. The next time I started the car I watched the needle, and it jumped up to about 150-200 RPM and froze. I tapped on the bezel (cause that always works in the movies), and nothing changed. So, I grapped that little plastic nipple looking thing in the center of the bezel and pulled out on it. Lo and behold the needle moved up to 700 RPM where the engine was idling. I feathered the throttle and it moved up to about 1200 RPM. I let go of the bezel, and the needle froze right where it was at. So, I just need to figure out how to get that bezel to not sit so tight against the needle and I will have a working tach. Never would have thought the fix would be so simple.