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Just got a factory tach out of an XR-7 gauge cluster. I put it in my cluster and it fits and looks great. There are two wires coming out of it. I hooked up one to the distributer side of coil. The other side to the ignition side of the solenoid. Works great when car is running, but if you cut the car off and try to start it again, it has no fire to the switch and won't crank. If you ground it, automatically kills the car. What do I need to do? Please help. All replys are greatly appriciated.
 

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Factory Tach

You need the original wire to the solenoid to stay there. That is used to start the car. The tach needs the wire from the ignition to the tach, then to the distributer side of the coil. All you are doing is putting the tach between the ignition and the coil.
 

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Hey Badcatt, can you clarify this a little better for the denser folks out here (yeah OK, me)?
I also have a fact. tach that I want to put in my Std. in the blank spot.
 

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Hey gearhead, I have a factory tach on it's way to me now and from what I am understanding here is all we need to do is wire the tach in series into the ignition so dont even consider running wires to the alternator, dist, etc. check out that boss 302 article it has a really helpful diagram that helps you visualize it. never mind all that other stuff about the other gauges.

If someone could clarify here it would be nice though knowing how to wire it both ways would be nice. I think i'd rather have it wired parallel if thats possible as a bad tach inline is a weak link.
 

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You cannot wire it in parallel to the coil, its a current sensing tach and HAS to be wired in series with the coil... If the tach fails in such a way to fail open it will kill the ignition. I added the tach cluster to my Mach 1, and didn't like the idea that it could cut the ignition if it failed the right way, so I wired a switch parallel to the tach under the dash. If the tach were to fail (which it never did), all I had to do was flip the switch to bypass it and re-energize the coil. If you don't want to do that, whatever connectors you use, get 2 of one gender and one of the other, wire the two terminals together on one of the connectors and use the other on the tach; tach fails, unplug it and plug in your jumper.
 

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Then again, do what I did for the answer and look down at the archives. Logan answered this question in 2001. Topic- "tach connections"
 

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I got a tach from TheRktmn, the tachs he makes has original face and mounting, but wires like a normal tach.
The tach he made for me fits perfect, wires easily and works like a dream :ylsup:
 

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OK, wiring parallel to me means wiring it how logan described it. Which way should I do it?

also, I do have an aftermarket Accell coil so what's this "inline ballast" that logan speaks of?

http://www.mercurycougar.net/forums/showthread.php?t=189



nosaj122081 said:
You cannot wire it in parallel to the coil, its a current sensing tach and HAS to be wired in series with the coil... If the tach fails in such a way to fail open it will kill the ignition. I added the tach cluster to my Mach 1, and didn't like the idea that it could cut the ignition if it failed the right way, so I wired a switch parallel to the tach under the dash. If the tach were to fail (which it never did), all I had to do was flip the switch to bypass it and re-energize the coil. If you don't want to do that, whatever connectors you use, get 2 of one gender and one of the other, wire the two terminals together on one of the connectors and use the other on the tach; tach fails, unplug it and plug in your jumper.
 

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As usual we have a conflict of information. Door A or Door B?

VERY easy to do. You just the wire from the positive terminal on the coil to the red wire on the factory tach, and ground the black tach wire.

Just be aware that the factory tachs are current sensing, if you're running an aftermarket coil, you need a inline ballast...
 

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Ckerian, if you do it that way (Logan's description) the tach emits smoke and the hands don't move. If that is what you expect from a tach then go for it.
 

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So Royce, does Badcat's description sound better then? I thought Logan's solution made more sense. Why would I see a smoke show?
 

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John,

Because the factory tach has a very delicate movement that cannot handle running 12 volts directly to ground without the benefit of the factory coil in series with it. Try it.
 

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But will it then work with a factory or factory style coil set up?
 

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What Royce said or smoke
 

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OK, good. I am glad I didnt do it. Thanks much Royce, it was something that was bothering me.

On a 70, this coil wire that comes out of my ignition, do I HAVE to cut it at the firewall where it's exposed by the fuse panel or is there a connector somewhere in the harness or in the column? looking at the ignition/block the wires are all soldered.
 

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