I got an Apexi tach and I am having multiple issues with it. First the needle bounces like mad when it reaches about four grand and also the tach light doesn't work. You're only supposed to plug it in and that's it, but for some reason the light stays on at all times.

 

You might have grounding ISSUES!!! My buddy had one is his riced out cavalier and it did the same thing. We took back to the shop where we got it from and they grounded it properly and rechecked the wiring. Or it could just be really shitting on you cuz it's breaking down.

 

Well it's only a couple of months old, and it's been like that since I got it. I'll ground it alot better (more). Thanx.