Tachometer misbehaving

[street]

Hi, tachometer start when start the car bounces a little and then stops, start car and it does it again, noticing has been changed, touched etc. I’m running illumination, told it may be the way it’s wired, but is been since 1989, yes it always been bouncy but works. Any suggestions?

[billwill]

Replace the capacitor inside the tacho? It has probably died of old age.