What is wrong with my tach?

[Portland68]

The factory tach I installed in my 72 K1500 seems to be working great up to 2000 RPMs and after that it isn't responsive - wondering if it is a bad unit?

Yes I am running HEI but it is reading idle correctly as well as light throttle, but it pegs out right around 2k whether I am going 70 on the freeway or trying to go 0-30 in a hurry.

I dug up an old thread about running a dedicated ground wire to the stud on the back but though this was a special case because it is sort of working. Thoughts?

[Curtb1971]

What I have found is most of the time with that issue it the needle gets hung up on the the face or button of the tach. Or it could be debris inside hanging up the magneto components. Either way you would have to disassemble that tach partially to check it out. Hope that helps out