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Discussion Starter #1
I am trying ot get the tach working on my car,apparently it has been disconected since before purchasing in 1981 and I was told it runs through the voltage regulator or something, I have MSD ignition so I know I cant go off coil, there is wiring in engine compartment not used with one lead plugs ins, what color is lead wire for tach? in engine bay. and where does it go, I have other tachs I can try but think it just needs to be wired right.
 

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To use the factory tach you will need a MSD tach adapter. P/N 8910 is for a points trigger (white wire on MSD) or 8920 for magnetic pick up. If you go to the MSD website with the P/N of your ignition you can download the instructions. That is were I found this info but I don't know how to post a link to it once I found it.
The 6AL box in my Eliminator has one and the tach works fine.
Mike
 

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I'm a bit new to all this myself, just got my '70 last July. But, my tach didn't work, and while researching it I learned that the Ford tachometers of that era were different from most aftermarket tachs. When they fail the ignition system no longer works, so most were bypassed when they failed. I sent mine to The Rocketman for conversion to a typical type tachometer. I got it back a couple of weeks ago but haven't had a chance to install it and try it out, my winter engine upgrades aren't done yet. Hopefully I'll get to try it in the next couple of weeks. If you have yours converted it will work fine with MSD or any other ignition system. I don't know if the stock tach can be made to work with aftermarket ignitions, I didn't research that since my tach was already inoperative.
That was a long way for me to say that your tachometer probably failed and was bypassed to allow the car to run.
Jeff
 

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Discussion Starter #4
I have 6al box on msd with white wire, what color wire is it in engine bay coming from tach?
 

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The engine wire harness section that picks up the water temp and oil pressure/light and + side of coil, the one with that plugs into the main harness, the + coil side goes directly to the tach, thats why if the tach goes bad you have no feed to the coil and no spark, guys jumper the tach plug when that happens, the other side of the tach feeds from the voltage regualtor hot side through the ignition switch, the tach is wired in series which causes confusion. Sorry I don't know the colors off hand.
 

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Discussion Starter #6
so for msd hook that wire up to white one on 6al box?
 

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The first thing you need to do is pull the dashpad remove the speedometer head and determine if the tach is even plugged in, it has it's own little harness plug back there. It kinda sounds like part of your factory engine wiring harness is bypassed, is there a bunch of shadetree wiring going on in the engine bay?
 

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I took cluster out and checked tach, is plugged in , I located the harness in engine bay just have to figure out how to correctly wire to msd, it has a white wire was told is for tach but someone had mentioned I will need a kit from MSD?
 

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I never had any luck with the tach adapters. But I did have tremendous success with the Rocketman tach conversion. I have one of, if not THE first, first generation XR-7 tach done by Bob and it has been flawless since the day I plugged it in. He converts the tachs so that they can be plugged into the tach port on the side of the MSD box. A second wire goes to power and a third wire to ground. Done!
 

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I took cluster out and checked tach, is plugged in , I located the harness in engine bay just have to figure out how to correctly wire to msd, it has a white wire was told is for tach but someone had mentioned I will need a kit from MSD?
Re-read post #2, Tinman posted the information you need if you want to use a stock type tach with an MSD.
 
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