Speedometer possessed by the devil

Fellow Super Dukers,

On the way to work today my speedometer started rambling. random numbers high and low. Then it could be stable for while, then suddenly drop 10 mph and up again. It has never happened before, slightly annoying I must admit.

Anyone experienced anything like that before?

Thanks in advance guys

From a few posts on here,,is you battery up to snuff BGC greased connectors connected

Had similar problem three times. First time was a loose battery connection outside of the cover beside the main fuse, second time a loose battery terminal connection, third time a loose connection behind the headlight.