S2 tachometer error

[ralleyquattro]

Hi guys,

I noticed that my S2's tachometer bounces between readings while cruising... sometimes up to 500rpm up/down.
Now that I noticed that, the tacho in the Coupe Quattro (7A) has started doing the same.
I hope they don't infect the rest of the fleet...

Has anyone come across it and is it an easy fix (capacitor etc)... I am handy with an iron, just need to know what to look for etc.

Thank you

[Bowie69]

Yes, come across it, think I fixed it, sort of, the other day when poking around replacing the speedo gear.

There is a tiny variable resistor on the side of the tacho when you have it apart, on seeing this, I thought it worth a twiddle to try and solve the same problem, except mine sometimes stopped working entirely!

I squirted with contact cleaner and gave it a turn with a small flat blade screwdriver and never had a problem since, except now my tacho only goes up to 5K on the limiter

I will dismantle and readjust sometime, by sitting on the limiter a while twiddling some more

[GreenMachine]

Same thing happened on my 7A 90 20v years ago. I thought someone said non resistored spark plugs could cause it. However, I've also heard of bad connections being the culprit. Marc at EFI Express would be a could point of contact as I know he's dealt with it before.