My tach will stop working very occasionally. I thought I had read something about this on the forum and cannot find it now.
Love my jag and the forum.

 

GLH, it is sounding like you have a broken solder joint on the backside of the instrument cluster. Unfortunately, the fix is to pull out the instrument cluster, get out a soldering iron and resolder any joint that looks fishy (ie, obviously broken or may have a "black ring" in the solder joint). if in doubt, resolder it. Just make sure not to join 2 or more posts together as that can lead to real heartaches.