throwback2 wrote:Source of the post On the back of the tachometer,you should see 468 cyl screw.Put a screwdriver on and go back and forth between numbers and then set back to 8.I had the same thing going on and I did replace the tachs a year later because they were different from each other.
I agree with the above Fred. It's a pretty common symptom as the contacts inside get corroded. That's why I asked what they were doing. The above is a common first thing to try in an attempt to repair before tossing them out. Some require that you depress the switch slightly before turning. Turn it back and forth several times in hopes of removing the corrosion. Not all units state "4,6,8" some simply have position 1,2 or 3 or some other OEM code so take note of the position before you start or you'll have to look up the position for an 8 cyl engine. Give it a shot.