Tach problem - disregard this thread !
 

Opps ! Disregard this thread.

related to post
http://forums.pelicanparts.com/porsche-911-technical-forum/186647-calling-all-tach-gurus-help.html


Dan,
I have my tach apart at the moment. The old circuit is bust, I have built a new one using an electronic breadboard and various components, so I have a reasonable knowledge about its heart.
From your description I would suspect either a broken internal connection, dry solder joint, or the needle movement is physically imparied somehow. I think a close visual inspection will identify the problem. Have a multimeter handy and check continuity

Depending on the model, taking the tach apart can be difficult. You may need to bend back half of the rim in order to disconnect the back housing. Take it easy.