In the last couple of days I have noticed a problem with the rev counter on my '92 CD B202. On start up yesterday the needle did not rise at all. Car drivng fine btw, 5-10 mins into my journey it started to slowly rise and eventually resumed normal operation. This morning it rose but steadily climbed to about 2000rpm.Then 5-10 mins into the journey it resumed normal operation. Car driving fine. Any ideas anyone?