[Tannaton]

I remember fixing the speedo on my 1989 440 Turbo several times. I got the car when it was 4 years old and it already had a new speedo head and a new cable had been run from the back of the cluster.

It would die but then start working again when you went over a big bump. Eventually fixed by re-soldering all of the connections, though I had to remove and refit the sensor whilst doing that so it may be related.