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Fri Jun 17, 2016 11:00 am

I'm trying to use a tach meter with my Pertronix distributor. I get nothing. I hooked up a test lamp on it is always on through rotation of the engine (does not turn off and on like when connected to points type ignition)

Thanks for any guidance or suggestions.

Mark

Fri Jun 17, 2016 11:16 am

use the coil.

Fri Jun 17, 2016 11:22 am

Tach signal wire goes to the negative side of the coil.

I run a VDO tach with my Pertronix SVDA, works fine.

Fri Jun 17, 2016 11:35 am

Sorry, should have been more clear; I am connecting the tach meter to the negative terminal on the coil (same for test lamp). The lamp always stays on. I do see a slight dimming as I rotate the engine. The Pertronix module has connections to the positive and negative sides of the coil.

Fri Jun 17, 2016 11:50 am

What does the tach do with the motor running? As far as I know, the test lamp is only used for a rough setting of the timing with points.

Fri Jun 17, 2016 12:14 pm

Tach shows no reading. I can place another vehicle and it works fine. Based on the action with the light, I'm just wondering if the electronic points work differently than mechanical points in how they ground the spark

Fri Jun 17, 2016 12:20 pm

Just what kind of tachometer are you using and what color of wires does it have?

Fri Jun 17, 2016 12:39 pm

It's a tach-dwell meter with signal and ground wire.

Fri Jun 17, 2016 12:50 pm

Pic

Fri Jun 17, 2016 1:44 pm

Biggest question... does you engine run? If it does not, then your points module could be bad and all these readings/results make sense.

Assuming your engine does run... Please you confirm you are NOT using the tach/dwell and test lamp at the same time?

Your test lamp, is it the LED type or does it have an incandescent bulb? You want the 12v incandescent bulb type with ~2W bulb. LEDs only flow current in one direction and the resistance may be too low.
You mentioned the test lamp goes dim and then brighter. Does this happen four times over two crank pulley revolutions (720deg). This could happen if the resistance thru the test lamp were very close to the resistance through the electronic points.

When using the test lamp, it is hooked up between the #1 (-) coil terminal and ground, right?. While the (electronic) points are CLOSED there should be very little current flowing thru the test lamp. It will be OFF. When the (electronic) points OPEN, all the current from the #1 terminal will flow thru the test lamp and it will turn ON. It may only be ON for a small angle of crank rotation as the magnetic ring triggers the point module.

That tach/dwell meter needs to be hooked up between the #1 (-) coil terminal (green clip) and ground (black clip). Have you tried both RPM and Dwell settings on that meter?

Fri Jun 17, 2016 1:48 pm

Ashman,

Yes, engine runs great.

Tach-Dwell or test lamp. Not at same time.

Incandescent bulb in test lamp.

It stays on throughout engine rotation (rotating by hand) which is what is mainly confusing me. I believe this is why my tach does not read. I've done this quite a few times on other cars with points. This is my first with the Pertronix point module.
Thanks for the help!

Fri Jun 17, 2016 2:29 pm

Which model of Pertronix electronic points are you running?

One other thing to check would be the internal resistance of the ignition coil primary windings. They should be in the 3-4ohm range for the Ignitor module. Though, I think the Ignitor II module uses a lower coil resistance. Check your instructions to make sure.

My understanding is the below instructions come from Pertronix on how to test their modules. It is not clear if this works for all models of their modules. Best to check their site for info on your module.

EDIT: Found this link for Ignitor ignitions:
http://www.pertronix.com/support/tips/

Fri Jun 17, 2016 4:51 pm

I have the same Pertronix and the same dwell/tachometer that you do and the meter works just fine. How have you connected the meter, i.e. green and black cables?

Fri Jun 17, 2016 5:41 pm

I connect the green clamp to coil negative, and black to ground. I'm thinking maybe I'm not getting a good ground connection.

Sat Jun 18, 2016 5:55 am

mjtracy wrote: I connect the green clamp to coil negative, and black to ground. I'm thinking maybe I'm not getting a good ground connection.

Perhaps start with cleaning all your grounds. In the engine bay you should be able to use the taillight ground next to the engine. If that doesn't work, your ground strap could be toast among other things like the battery ground. Do you have any other quirky issues?

Sat Jun 18, 2016 6:12 am

I have the same meter and just ground it to the bolt that hold the coil onto the cooling shroud.

Sun Jun 19, 2016 8:22 am

I like to use the clips that hold down the distributor cap as a ground point. The distributor body is a good ground source and conveniently located centrally on the engine. Just watch out for the rotating fan belt.

Sun Jun 19, 2016 11:16 am

I usually hook my ground to the ground screw on my generator.