I know, I know. There are a million posts about this same thing. But the thing is, none of them really tell you how to do it! I have this aftermarket tachometer that I want to use. It's got 4 wires: Red, Black, White, and Green.

White: Dash lighting
Red: Switched 12V
Black: Ground.
Green: Signal wire from tach port, distributor, or "negative side" of the coil.

My problem is with the Green wire. What is the "negative side"? Surely I wouldn't attach the green wire to the big fat wire that goes from the coil to the distributor right? I really don't see where a "negative terminal" is, or how on earth to attach a wire to it. My truck has the EEC-controlled ignition system (TFI-IV).

I know there is a way to swap in a factory tach/speedo gauge cluster and I don't want to do that. I know there is some tach signal wire that is already coming through the firewall in a bundle of wires but who the hell knows how to find that?

 

I just added the green wire to the one wire that is closest to the firewall. It works like a champ. No problems since i added it. Glad i did.

 

Could you be more specific? Some of us tard's need a picture. By the way, I went to the California Smog test and they actually put a timing light on my truck. And flunked me cause the rubber around my gas caps showed some cracking. I was flunked at another place cause I didn't have a dust cap on my Charcoal canister. I was flunked at another place cause I had a clear hose on my vacuum hoses. Cali is really trying to get our Ford trucks off the road. Lucky I bought two gas caps at the Auto store next to the test site. Also got a black hose for the air cleaner. They let the dust cover over the charcoal canister go. But that was because I use the test station for all my rigs. $65. I said credit card if I flunk and cash if I pass. (good advice in these crooked political times) Now I am trying to find out how to put an aftermarket Tack in the empty space in the middle of my dashboard because it needs to be timed and it is timed at a specific 8 degree's before top dead center, at a certain RPM. Not having much luck with instructions on puting a tack in that empty slot. 1981 302 built in Cali. One would think that it would be a slam dunk because the console has the space for it. . But as John Balushi used to say. Noooo-000. You can't get there from here.

 

The coil has two wires. If you slip the wire terminal off, you might see the coil marked "-" and "+". I used a scotchlok to attach my wire for tach.

I don't have my wiring diagram handy to tell you what color is what. I put an aftermarket tach on my '95 and '89. No big deal.

 

Looks like the Tan/Yellow wire is the one you need to tap onto.

 

So I almost didn't buy it but I did and started installing it, long story short I forgot to disconnect the battery and had everyrhing hooked up lights on the tach working. I put the quick splice on and when i started my truck my volt, preasure and temp guage are not reading and from what I can see my fuses look fine. Any suggestions please?