Problems with Autometer Tach

[trbodon21]

Recently my Autometer tach has been acting weird. It doesn't always read the correct engine speed. It jumps around on occasion from 1000 to 6000 RPM when car is idling, cruising, or at wot. Then it will act normal again. I checked wiring and everything seemed to check out ok. Also sometimes it will seem like it gets stuck at a different points on the tach like at 2000 rpm when I am idling when the scan tool shows I am really at 1000rpm. What can cause this?

 

[slamming 6]

check your ground wires ,try the tach in another car and see what happens.