New Tach Not Working

1350 Views 9 Replies 5 Participants Last post by shovelrick, Oct 2, 2021

xk49

Discussion Starter · Oct 1, 2021

I just installed my new tach from Ground Up on my 1964 chevelle and it's not working. The car has had the points replaced with a Pertronix Ignitor, but thats down stream from the coil so that shouldn't matter, I think. When I start the car the tach needle blips just a little then settles back down to nothing. Rev the car and it doesn't move.

Here's what I have done:

Red positive wire from tach is directly attached to the fuse box IGN ON post. I've tested the post with car off and no voltage. Turn car on, voltage is correct. So, I know I have a good power source. I tested the post with the same ground location as to where the tach is grounded so in know it's a good ground location.

Confirmed the brown wire is attached to the negative side of the coil and onto the "-" post on the back of the tach.
Confirmed the ground wire is on the "S" post on the back of the tech and is securely attached to dash metal(same location as another electrical ground).
Confirmed the red wire is connected to the "+" post on the back for the tach and to a power post on the car that's on when the car is running?

First time installed one of these, but it seemed pretty simple and I don't know how to trouble shoot beyond what I have done.

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shovelrick

· #2 · Oct 1, 2021 (Edited)

You probably need a resistor on the Tach wire, I went from an Ebay HEI to a Pertronix Flame Thrower III with digital rev limiter and my Super Tach II wouldn't work without a .5 watt or Ohm I don't remember but I have a box of them and can send a pic, heck I can mail you one if you want, I ordered 100 when I thought I was ordering 1 LOL, gave 20 to my engine builder 🤣Also I'm pretty sure the red from Tach goes to Tach on dist. not fuse box, there is a wire that goes to a light circuit so when you turn your head lights on the Tach lights up, can't think what color my Tach wire is that goes to dist. though