Speedo Fault

[CornishSilver]

Hi, hoping someone has the fix for this......My speedo is all over the place, sometimes it will read approximately ok and then at times it will be showing 70-80mph when I'm doing 30ish, it tends to jump up more so when the accelerator is pressed. Im not to bothered about an exact speed reading but it would be nice to have a general idea of say +/- 5mph, any ideas or is it a new speedo? 1970 lhd if that matters.

 

[triothreetrio]

It could be the cable on its way out