Need to know what is happening, but I suspect a faulty earth at the back of the dash if it's not just one gauge that is playing up.

All the instrument earths are taken to a single point behind the dash (or they used to be on older cars).

Cheers,

Graham (G4FUJ)

Sold L44FOR 4/4 Giallo Fly
'11 MINI Countryman Cooper D All4
'90 LR 90 SW