Speedo madness

Hi,
An odd one here.  So the speedo in my MK1 goes a little mad when i'm doing anything over 30MPH.  Just driving down the road up to 30MPH is fine, anything faster than that it read 50MPH plus.  While i was doing 60MPH down the A3 it way saying i was doing 100MPH.
So far i have pull out the speedo cable which has been replaced with a new one and i have replaced the drive end too (red end) on the cable too.
Some reading around this is saying that the speedo is broken & i'm looking at a replacement, due to a band ground.  Now before i start pulling ground out all over the dash to get the speedo dials out i wanted to see if anyone else had any points?

A bad ground isn't the issue, if you have replaced the cable and the drive gear.  Then the speedo is the culprit.

How-ever I don't know if you have a oxs light on your dash, but depending on the year your cable could go into a counter box, then out of the counter box to the speedo.  

If you have a one piece cable to the back of the speedo, then it is the speedo.  

If you have the counter box, then you might want to get a one-piece cable out of a "Cabriolet of the 90's" or Diesel's and take that out of the loop.

It sounds as if your return spring is broken, or is slipping and giving the needle a boost.

When I changed the cable it looked to be one complete cable running from the top of the gear box to the back of the speedometer..
The car is 1986 mk1 Cabriolet 1.8 GTi
I don't think it's got a box unless this makes up the speedo..
Does this help firm things up what it might be ??


Sent from my iPhone using Tapatalk

yep, I would say speedo.