Speedometer Needle Randomly Working/Not Working

[JorEl]

Won't move for weeks then I'll be sat idling and she'll bounce up to 150MPH and fluxuate there for a while - Screwing up my mileage in the process!

Have cleaned the Red (LED?) at the diff but still having this problem.

Anyone?

[JorEl]

Ok cheers, speedo sensor... Is located??