Tach Wiring..??
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I would try plugging it in first and foremost, and save some work if you can, unless the connector physically cannot connect to the cluster. I bought a cluster with a factory tach from eBay, then opened up the cluster and removed the tach, installing it in my own factory cluster after removing the "blank" spot. I then wired it up using the four posts on the back of the tach that protruded out the back of the cluster. That way, I kept same mileage, etc. As far as identifying the "tach" post on your coil, give your coil a look over - I bet on of the posts has an indentifying mark near it that literally says "TACH". If it doesn't, let us know so we can work out how to tell the difference.
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Laughing Gas
Joined: Nov 2006
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OK...Took the ckt. board off that came on my tach...4 Positions...Upper Left...C....Lower left...8...Upper Right...G...Lower right...B...Pt#..EOTF-17360-Y...Also has AA in ink stamped on back....I'll get it working yet !!!.....j
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Did you try just plugging the whole cluster in? I bet yours would just work. If you want to remove the tach from the cluster, remove the clear plastic cover from the front of the cluster, then remove the four nuts from the tach posts on the back of the cluster. It will easily pull out of the cluster at that time. There's no need to remove the printed circuit - if you remove the printed circuit, the whole cluster is not going to work if you were to plug it in. Everything in the cluster relies on that printed circuit to operate.
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Laughing Gas
Joined: Nov 2006
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JM....All I have is the tach...and 4 nuts that are holding it to a piece of printed ckt...and there is a small metal piece...I'm guessing a resistor, maybe....That;s it...My truck is 84 ...351//auto...gauges....Would there be a ckt board already in my truck that I can attach the tach to with the 4 nuts,,,since I have the gauges, but no tach...Is it wired for one in case it was ordered ?....jv
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From: Campbell River, B.C.
Originally Posted by ozark1
JM....All I have is the tach...and 4 nuts that are holding it to a piece of printed ckt...and there is a small metal piece...I'm guessing a resistor, maybe....That;s it...My truck is 84 ...351//auto...gauges....Would there be a ckt board already in my truck that I can attach the tach to with the 4 nuts,,,since I have the gauges, but no tach...Is it wired for one in case it was ordered ?....jv
The coil will have a connector with the label TACH TEST on it, this is your signal for the tachometer and I simply spliced into it at the coil.
The four contacts should be as follows, "C" is to this ignition coil, "8" is the secondary ground for an 8 cyl engine, "G" is the primary ground, and "B" is the 12V power supply -connects to a "hot in run" 12v source. You can test this wiring under the hood with a few small jumpers to see if it works.
To install the tach I had to open up the cluster assembly and remove the filler panell where the tach is supposed to be, the tach simply slides into the cavity and there are already four holes in the back of the cluster for the small studs on the tach. I too didn't want to mess with the mileage and replace the whole cluster.
Oh and the small metal piece you discribe, if its aproximately 1" long and 3/8" wide I'm guessing its the regulator for the cluster guages, you may want to hang on to it as they can be hard to find.
Last edited by David85; Jul 3, 2007 at 03:51 PM.
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Laughing Gas
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That's the piece...OK...I'm going to pull the panel...If there is not a place to simply attach the tach to an existing ckt. board...and bolt it to the blank spot in my dash...I will wire it...Thanks to all...Couldn't...or wouldn't have tried it without the help of the board....Jv
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That's what you'll have to do. Even though you have all the other guages, you'll notice the printed circuit on the back of your existing cluster will not be connected to the four stud for the tach. I thought you had bought a whole new cluster, not just the tach. This is easy, though. David85 is right on about how to wire it - this is exactly what I did. I like having the stock tach much better than a big aftermarket one bolted to the steering column. Let us know how it works out for you.
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From: Campbell River, B.C.
Originally Posted by ozark1
Working on it...Where should I attach Primary Ground ?...and Secondary Ground ?...J..I assume that any 12V.. always hot.. wire is OK for "B"..?
The ground can go to the body sheet metal, I would avoid using the metal parts that support the dash or steering column, as they are ofted poorly grounded. Primary and secondary ground can be connected on the back of the tach and then share the same ground at the firewall or whatever is is easy to reach.
Last edited by David85; Jul 4, 2007 at 03:18 PM.
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Thanks JMKelly for the TACK pin-out info
Originally Posted by jmkelly
Here's how I wired mine up. The post on the rear of the tach labeled "1" should run to the "tach" post on your coil. The post labeled "8" is a ground IF you have a V8. If you have the I6, then leave this out. The post labeled "G" is a regular ground, and the post marked "B" is a switched hot wire. I had to wire mine this way due to a butchered electrical system from the previous owner. If your electrical system is intact, then try to just plug the whole instrument cluster in - it will probably work just fine.
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