Wiring Tach

[Mike snyder]

I am trying to figure out wiring with out spending half a day testing leads and squinting at the wiring diagram.
So here is what I've got. I have installed a Pertronics electronic ignition. I had the tach rebuilt by Nisonger to work with the electronic ignition. The tach now has three wires in the back. One is the ground (obvious attachment). The second is attached to the distributor side of the coil. The third is a 12 volt fused power lead.
Here is my question. Since I no longer need a signal generator loop can I cut the loop wire and use the side that goes to the ignition switch for my fused 12 volt power source and the other end that goes to the coil for my signal?
Thanks!
Mike Snyder

 

[Tom H]

Mike , I understand coils , ignitions, and Alpine tachs very well. But I do not know what mods Nisonger made to your tach so it is impossible to know what connections are required.

Did Nisonger not include installation instructions? Are you sure the one connection you describe goes to the distributor side of the coil? It seems reasonable that the wire from the ignition switch can go to the "fused 12 V connection" , but using the other end that used to go to the +12 V side of the coil and connecting it now to the distributor end of the coil makes no sense to me . If you do that what circuit provides 12 v power to the coil???

I am guessing that the other end should go to the + 12 v side of the coil and NOT to the distibutor side.

Tom

 

[Mike snyder]

Hi Tom,
Good to hear from you. I used your Tach Rebuild Manual for a reference for my posting. So, Nisonger did send instructions. There were three points.

1. Attach the ground to a ground point.
2. Attach the white wire to the distributer side of the coil.
3. Attach an ignition switched fused power lead to the spade terminal on the Tach.( the spade terminal on the Tach is labeled "+12 volts")

In my post I forgot to mention that I am converting the car from positive ground to negative ground and the Tach was rebuilt accordingly. The dash is out of the car. Also, the distributor was rebuilt with a two wire Pertronics electronic ignition(red to + on coil, black to - on coil).

In your manual on page 11 the right hand picture shows the looped ignition signal wire. I am wondering if I cut that wire will the end that runs to the ignition give me a fused positive 12 volts? And can I use the other end attached to the distributor side of the coil for my signal?
Let me know your thoughts.
Thanks,
Mike Snyder

 

[Tom H]

Mike, Glad to help. But I am still puzzled about what the tach looks like now and how it and the ignition is supposed to work.

From your description I take it that the steel C clip on the rear is no longer there or no longer used, is that correct?

And I am guessing that the +12 V spade terminal is the original one, or maybe a new one.

And there are two wires protruding out the rear of the case, a white and a black. Or maybe the black wire is attached to the case . Correct?


Now inside your car, behind the dash, assuming a stock wiring harness, there should be 2 white wires near the tach opening. One should have a spade lug on it, that's the original wire used to power the tach and you should simply reconnect it to the +12 terminal on the rebuilt tach. The other white wire is the one that loops thru the plastic clip and thus also thru the c clip on the original tach. That's the wire you see in my photo on the right side of page 11. I would NOT cut this wire as it needs to continue on to the non distributor side of the coil. If you cut this wire here and use it to connect the new white tach wire to the dist side of the coil you will have no power going to the coil (nor to the Pertronix!) ..So instead you will need to run an additional wire from the white wire on the tach to the dist side of the coil.

Note that in the stock Alpine wiring harness, the white wires are all Switched (by the ignition switch), but are NOT fused. If you wish you can add fuses in line at various points or add some additional fuse blocks. But that's a whole 'nother topic. I think Paul A and Bill Blue will be covering that at a tech session at the Invasion.

If you want to talk about this send me your phone # via e-mail (not PM) . Just click on my name and choose "send an e-mail"

Tom

 

[Mike snyder]

Thanks Tom!
Your assumptions were correct. I am going to run some new wires with an inline fuse. I think this will be the easiest thing to do. The back of the Tach has a white wire for the signal, a spade lug (black) for the +12 volt and a ground wire. Internally I have no idea what they have done.
Mike Snyder