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New Tach Not Working

1346 Views 9 Replies 5 Participants Last post by  shovelrick
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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Went back to TRIPLE check the connections and low and behold the problem is on the tach itself. The ground post is janky. I thought something was weird when I went to put the wire connector on that post and there was no locking washer like there was on the other two. The post spun when I tightened down the nut to hold on the wire connector, and now that's it's actually in the car I can wiggle the post and spin it. The bottom nut is tight but the post is still loose. I spun the whole post setup like a half turn(with my fingers and not a wrench), started up the car and the tach is now working. I think something or someone over torque that post from the factory and whatever it is touching inside is now compromised. Don't really want to take it back out to return because its a pain in the ass. Maybe I'll get lucky and my half turn will stay put.
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