Faulty Spedometer in 1994 Honda Civic Hatchback

My 1994 Honda Civic Hatchback (stick shift with 180k miles) has a faulty spedometer. The spedometer works ocassionally, but usually stays at zero. Once driving on highways it sometimes jumps up to 80 mph, where it will stop for a couple minutes then drop back down to zero again. What needs to be replaced?