tach issue

[terzmo]

Bought a mopar and it has a super pro tach...didn't work...connected the wires "properly" and it works...sort of...at idle the tach just goes to zero...rev it up and it works when the rpms get around 1400 or so and after that seems to be fairly accurate at speed vs rpm. What is the issue about crapping out below 1400 plus or minus ?

 

[tallhair]

Does it have a 4-6-8 cylinder switch? If so is it on the right setting?

 

[terzmo]

no...good thought though