Bouncing tacho needle

[trigolf]

Afternoon all,

The original cable driven tacho on my Vit has suddenly got unstable - i.e. the needle bounces up and down a lot more than it used to, even at idle speed.

I have oiled the drive cable and it all appears free to move/rotate. The needle moves freely with the gauge off the car and returns to zero, if I shake it gently, so at this point I don't want to start dismantling it. My suspicions are that it more likely to be the cable than the gauge. Do they get tired/stretch over time?

[NonMember]

The cables can fail in a way that produces that bouncing needle behaviour. It's normally a strand of the inner cable breaking free, which then catches on something and makes the motion at the instrument end jerky. Whether you'd feel that catchiness with it disconnected isn't always clear.

You can also get jumpy needles due to a bit of grit in the gauge mechanism, but that's normally associated with it reading very high, too.

[Pete Lewis]

and the cable lengths can can go wrong  if there is poor engagement in the back of the head due to the nner being a bit short 

you can with some grips  rotate the outer case spiral wrap casing it will screw longer or shorter and change the protrusion of the inner drive 

this may help   it may sound daft but this is quite a sensible  fix 

Pete