Tachometer Wiring

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Tachometer Wiring

Postby NCfrogeye » Fri Sep 29, 2006 1:33 pm

I need help. I'm trying to wire my electricial tachometer, but I don't have any idea which terminals to use for the wires. Also, my wiring diagram calls for three wires, white in from ignition, white out to coil, and green from fuse box; but I can only see two terminals, one spade type and one post with a nut. There are also two flush mounted screws adjacent to the spade terminal, but they don't seem to be for making wire connections but rather holding something internally in place.

Can any one guide me on this. This is the last thing I need to do to complete a total rewire.
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Postby Frogarri » Fri Sep 29, 2006 6:20 pm

A little more info would be nice, like:
What year/model tach
What year car
What wiring harness
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Postby NCfrogeye » Sun Oct 01, 2006 8:57 am

The car is a 58 Bugeye and the wiring harness is the correct one for this car (i.e. no connections for an electrical tachometer). I decided to use the later model (electrical) tach because it is in much better shape than the original one that came out of the car. I have no idea what year or model the replacement tach is. My plan is to splice into the white wire leading from the ignition switch going to the coil.

My problem is that I can't see how to attach the white wires. The back of the tach has a small diameter threaded post with a nut and two very short rounded spade-like projections on either side of the post (too short to attacht standard female connectors). Is there some type of special fitting that goes here to which I attach the white wires?
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Postby Frogarri » Sun Oct 01, 2006 10:35 am

NCFrogeye,

What is the model # of the tach? Look on the face of the tach there should be a model # just below the arm, like RN 2312/01 or RV1 2401/00B, etc..
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Postby NCfrogeye » Sun Oct 01, 2006 5:21 pm

The model number of the tach is RV12401/008.
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Postby Frogarri » Sun Oct 01, 2006 7:16 pm

Okay. You have a tach from a Mk-III Sprite or a Mk-II Midget. It is a impulse type tach that should have a block on the back which the white wire runs through making a loop that triggers the tach. Only two wires actually hook up to the tach, a green wire from the fuse block (same green wire that goes to the fuel gauge and the windshield wiper motor) and the white wire from the ignition switch to the coil. From your earlier postings all you have is a spade connector (green wire) and a post & nut. The post use to hold the block that had the plastic/nylon piece that the white wire would make it's loop through. Without the block and it's little cover piece you cannot hook it up. The direction of the loop will be determined by the ground on your car, one way for positive ground, the other way for negative ground. If it works when hooked up your fine, if it doesn't work just reverse the direction of the loop. Your high beam indicator light and panel instrument light will just plug in as usual.
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Postby NCfrogeye » Mon Oct 02, 2006 8:18 am

Any ideas where I can obtain this plastic block that holds the white wire loop? Can I fabricate one?
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Postby NCfrogeye » Fri Oct 06, 2006 3:03 pm

Found a used induction block on an old scrap tach. Thanks for all your help. :D
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Re:

Postby bfleissner » Mon Oct 12, 2009 10:29 pm

Frogarri wrote:Okay. You have a tach from a Mk-III Sprite or a Mk-II Midget. It is a impulse type tach that should have a block on the back which the white wire runs through making a loop that triggers the tach. Only two wires actually hook up to the tach, a green wire from the fuse block (same green wire that goes to the fuel gauge and the windshield wiper motor) and the white wire from the ignition switch to the coil. From your earlier postings all you have is a spade connector (green wire) and a post & nut. The post use to hold the block that had the plastic/nylon piece that the white wire would make it's loop through. Without the block and it's little cover piece you cannot hook it up. The direction of the loop will be determined by the ground on your car, one way for positive ground, the other way for negative ground. If it works when hooked up your fine, if it doesn't work just reverse the direction of the loop. Your high beam indicator light and panel instrument light will just plug in as usual.



so the ends of the wire loop on the back in the plastic housing don't connect to anything?

this site (http://mgaguru.com/mgtech/electric/et202a.htm) shows the wire connecting on both ends. I know i have to resolder 2 connections inside the tach, but I'm just trying to understand what wires outside connect to what.

thanks
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Re: Tachometer Wiring

Postby bfleissner » Thu Oct 15, 2009 5:42 pm

Still looking for help...

Going through some of the boxes of stuff that came with the car I found the receipt for a Petronix coil. Checked the coil out and there's a red and black wire that come off of it and go to the ___________ (not sure) and two white wires, one with a black stripe that go no where (just hanging) that also come off the coil.

thanks
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