yamaha ox66 sx250 2001- tach wont read

[jhincman]

Hello All, looking for some help diagnosing my tachometer- i swapped in a good working used one and have the same issue.
Issue is : light up, hours read, says "ZERO" and I get voltage on the green signal wire of whatever the current battery is- up to 14v. but wont register any changes on the tach numbers- i checked all dip switches as well. Any help would be appreciated, Thanks!

[99yam40]

info on tachs might help.
need to make sure the tach are getting the proper signal to them