Well...

So I was hoping to not have to send this tachometer back but I could no longer take having its random operation. Sometimes it would work sometimes it bounced around and sometimes it did nothing. Finally during one of the times it worked it tapped on the housing and the needle just bounced around. Some buddies of mine and I determined had to be something loose inside, and that it shouldn't be my responsibility to take it apart. So I removed the tach and sent it back with a note describing its operation and told them to test. I also told them that if it worked to tap on housing to see needle bounce. I also told them to please test the next one before sending be another one.

We will see what happens I will keep anyone interested posted