Erratic speedo needle!

[daveparry]

I know this has been done before but I can't find the answer, my speedo needle stays stubbornly at 0mph until I get going a bit then it jumps to 40mph and for a while it appears to behave itself but then once I get to motorway speeds it is waving all over the place then steady then wavey.

I have checked the trigger wheel gaps aren't clogged and cleaned the face of the sensor, what else can I do?

Do Speedycables fix this sort of thing?

[EGB]

Speedo sensor on prop shaft or on gear box may be on its way out or electrical connections for this need a clean and adjustment.