Ford Repair: 72 f250 pertronix/autometer, autometer tach, flame thrower

Question
72 f250 390cid
I have rebuilt the engine and installed a pertronix ign with flame thrower coil. I have also installed an autometer tach but can not the tach to work properly(sometimes it seems to be OK but then the needle will just start flipping all over the place or just reads 0 and doesn't move at all). I have spoken to both autometer and pertronix techs, they suggested installing a capacitor which I tried but when it was installed the tach sat on 0 and would not move no matter what you did. No one seems to have the answer, just wondering if anyone else has had this problem and if they were able to fix it.

Answer
Mike,

I recommend checking your ground as you may not be getting proper grounding. Obviously you are getting interference from somewhere. Also, if you have the ability to, try a different gauge as you may have a bad one straight from the factory (does not happen often but it is possible and I have seen it happen). If that doesn't work, please let me know and I will try to help you out further. Good luck.


Ken