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Discussion Starter · #1 ·
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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1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
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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 馃ぃ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
 

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Discussion Starter · #3 ·
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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I would put the points back in and if you want more power put a CD box on it. The points will last forever only triggering the CD box... The points / CD box is one of the best ignitions going..
 

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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.
Can I assume your tach is from OER? If so it may or not work with the Pertronix ll or lll. Both are intelligent and pulse shaping modules that can vary the dwell and also increase the spark, provide multispark and rev limit. They are very nice modules. They are designed for full 12 volts which factory or reproduction tachs can't handle. As Rick says sometimes it a simple inline resister or resistor and capacitor (RC circuit) to resolve. You can also buy a factory type filter that ALL GM cars used when HEI came out because they also ran on 12 volts without a resister wire. Again the tachs couldn't handle Full 12 volts. In my case nothing worked with my 68 and Jegs dropped their dime and sent my OER to Redline Gauges in Ca and converted the guts and problem solved. I now have a digital accurate tach that looks factory.
 

Premium Member
1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
Joined
11,604 Posts
This is the resistor I used, I have 79 spares I carry in my glove box :oops: JK :LOL:
Font Material property Electric blue Paper Receipt
Circuit component Light Blue Musical instrument Electronic instrument
 
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