Ok so I have a Mallory ignition box and an autometer tach. How do I hook this up so it will work. I have tried: -Running it like the instructions say, attach the yellow wire to the tach = nothing -Running a wire to the (-) side of the coil = nothing -Running a wire to the (+) side of the coil = crazy jumping around of pointer. Thats all I can think of trying. Can ANYONE PLEASE chime in about how to wire this. I called MSD cuz I thought I needed one of their tach adapters, but the guy there says all it does is "spike" the signal. Thats it. I feel like the problem is greater than that. Does anyone have this box and an aftermarket tach? Thanks for the help.

bump....out of desperation.

Anyone, please help. I can't get through to the mallory tech, or the summit tech lines....

I dont have an ignition box yet so I dont know if it helps. I have a autometer tach. I ran a green wire to my dizzy, black to a ground, red to fuse box and a white wire to fuse box for the light.

thats what i did too.... before the box, when it all worked.

Yellow wire? What happened to green, red, black, and white? Hooking to + side of coil, not a good idea. Keep trying the help line at mallory.

I have. Still no response.

The white is for the lights. Then they have their own black.

The tach's "important" wires are not colored. The tach just has studs. You attach whatever you want. THIS IS NOT A STOCK CAR WITH STOCK WIRING. I can't stress that enough. The damn color has nothing to do with anything. The neg. side of the coil does NOTHING... The + side at least makes it just around. Maybe I have a bad ground, that is what automoeter's website says sometimes happens.

I called MSD, and the tech guy there said many many applications go to the + side of the coil. Do you have any evidence that they are giving me bad advice sqzbox?

I am gonna call automoeter tech now. Thanks for any help.

-Dennis

I'm not familiar with auto meter or MSD but, stock or full race I have never heard of anyone getting an RPM signal from the + side of any coil. The + side of the coil requires a 12V connection that energizes when you turn the ign. on to start the engine and run thereafter. I think the guy at MSD has been sitting behind his monitor too long.
If you can get the tach to work right off the + side then either the coil is marked wrong or I have learned nothing in 40 yrs. of building cars. Something definatly is wrong. Have you tried testing all connections with a continuity tester with key on then key off?
I'm pretty sure about this one and if I'm wrong, I guess I have a big pair of short's to eat but first, their going to have to show me!

SQZBOX

Well, it is 100% impossible to have the coil misslabeled cuz I had it hooked up before the box was in and the tach worked fine. Right off the - side of the coil. Now it doesn't do anything. I have not touched the dizzy appart from pulling the chip to attach the box.

I don't know what to tell you, the + side makes it move and the - doesn't. I can take a video of this if you don't believe me. I understand the ignition system pretty well. I know what you mean when you say it makes no sence... Imagine how I feel, its happeneing to my car, THAT I BUILT from the ground up.

By the way I still can't get to mallory. Oh and the Autometer guy says that the tach can take " any 12V square wave" I asked, " what about + or -" He said " Doesn't matter."

Ok then, hook up the old coil, connect the tach wire to the + side and tell me what it reads. My wifes eatable panties are starting to look pretty good. I think what the Auto meter guy is saying is hooking it up to the + side won't blow the tach, not that it will work on either side. DAM can I get any help here? anyone?

I would just go back to stock style with the chip, if the box didn't make the motor run so much nicer. I really want to keep it. Not to mention the rev limiter.

Starting back at square one here and trying to summarise.... BOTH posts on the coil do not do what I need. One makes it do nothing, the other makes it jump around. We also know for a fact that the tach wire comming from the box does nothing. THIS IS WHAT IS KNOWN. Now what can be the next step in solving this problem????????????????????????????????????????

Mallory

Which ignition box do you have?

The Mallory 6-AL.

OK...

What distributor, and what coil?

Mallory 85 Series HEI Distributors: MAA-8548201C - summitracing.com

The standard Mallory HEI with the cap in coil that is round.

It has a 4 pin module. I wired it just as it says in the instructions. I think the one thing I dind't do was go all the way back to the battery for the main (-). I just used a nice chassis ground. Same for the +, I went to my painless MASI fuse. The fuse is directly connected to the battery though.

Looks reasonably straightforward then.

Getting the battery for the amplifier from a fused circuit shouldn't make any difference. That ought to be OK.

The tach should have at least 3 terminals: 12V, signal, & ground. 12V should go to a known good source of switched ignition (pink wire circuit); ground, to any known good chassis ground; and signal should hook to the yellow wire from the 6-AL. If the tach has a 4th terminal for lighting, hook it to your dash light circuit (grey wire).

Is that how it's hooked up? Are you sure you have known good +12V and ground hooked to the tach? Like, checked it with a test light?

I have bot used a test light, but all my other guages are getting their 12V from a special terminal I made specifically for this reason. I knew I would need a 12V switched sorce. Remember that I wired the entire car myself. All other guages work perfectly, so I know that the 12V that the tach is getting is good. The only inigma is the damn yellow from the box.!!!!..!!!..!!!

Well, 2 things then:

Either your tach isn't getting its 12V & ground; or the tach is incompatible with the Mallory's signal or it's defective.

The yellow terminal should have a square wave on it, one pulse per cyl firing. Any of the usual ways of checking that should work, like an oscilloscope. Kind of a no-brainer, electronically.

For another quick check, try a different tach. Borrow one from a friend or something. You can hook it up with Radio Shack alligator clip leads, just to see if it works.

Alternatively, you could try hooking your tach to the "Tach" terminal on the distributor cap. Although that may make it read WAY high, I don't remember whether that ignition is a multiple-spark thing or not, I think it is though. But at least that will tell you if the tach itself is at least working. And of course, the tach should read right, if you hook the dist up without the 6-AL with the tach connected to the dist cap Tach terminal.

Try to split the problem in half: is it the tach, or is it the ignition. If the tach works with the box disconnected, it's the box. If another tach works when hooked to the box, it's the tach.

Yeah. I hooked up the tach to my moms carolla. It worked fine. I just spiled into a random wire coming from what looks like the dizzy. It was a black wire, so I figured it was the coil grounding. And it was! Very lucky. Anyways, the tach moved just as it should. So I know the tach is fine. Maybe I can check the yellow wire, but how would I ever do that from home? I have no idea. I do work with some electrical engineers, so I guess I can check with them. This really sucks. I am this close --->[ ]<--- to just buying the "tach addapter" that mallory sells and hoping for the best.

I guess I will look into trying to find a way to check for the square wave.

There is a Mighty Mouse! Thaks for the assistance! I still think the Auto meter guy stuck too many hair pins in the wall sockets.

Well regardless if the Autometer guy was retarted or not, the facts still stand and we have yet to hear from anyone with an autometer tach and a box. This is insane. I see these tachs on rice rockets all the time and in people's pics of their cars... they are everywhere. I am so suprised no one has chimmed in that has a box and a tach!!!!

I feel like this is more of a BUMP. Please give any advice relating from prior experience.......ANYONE!!!

Try posting your "Q" on the electronics forum and see what you get. Not trying to send you packin', but alot of elect. freaks hang out there! If you find anything out, come back and update us old general engine guy's. OK?