Tachometer wiggle, Just started yesterday Options

[BiG bOgGs]

Yesterday while on the way to and from work my tach needle started to wiggle upwards from its usual reading of about 3400 rpm. Until yesterday I had no problems at all.

On the way home I noticed that if I was under moderate acceleration or deceleration the tach read steady. When I was cruising at a constant speed is when the wiggling would start.

Any suggestions on how to track down the problem and fix it? (IMG:style_emoticons/default/poke.gif)


Jim

[Spoke]

Yep, no overshoots. Back in the day everything was analog and the driving signal (the points) were brought right into the unit with minimal if any dampening. The needle is so free moving that when you rev the engine, the needle rapidly goes to where it should be then keeps going because of inertia, then drops below, then back up; basically oscillating and finally ending up at the proper RPM.

Nowadays the spark unit is digital and microcomputers calculate where the needle should be and put it there. No bounce, no overshoot.

The 2200uF cap dampens or averages the signals from the points and really dampens the spikes and removes the overshoots and undershoots.