Tachometer Dead

I understand the Mercury Villager is a Nissan Quest with different trim. So can anyone help me with this one? The tach on my 95 Villager became intermittent several years ago and now rarely comes alive. The car runs fine and I have tried to get wiring diagrams/info on how the tach is driven from the dealer but the said they would probably need to replace the instrument cluster. There must be a loose/burnt connection or some sort of sending unit. Does anyone have any ideas?
Thanks