Speedo sometimes out?

[Ron173]

G'day all,
On my DX22 3.2 4x4 manual diesel QD32..

Speedo sometimes reads low, like 80 at 100, I use a heads up.

Anyone know if its a sensor or easy non expensive fix?

cheers

 

[brendo]

I have a similar problem with mine but the not a 20 k difference but in the last week it sometimes drops to 0 as well as the revs and the temp goes all the way down