Aftermarket Tach Instal?

[SRH916]

Hi, I have just bought a cheap little tach just for tuning, and to see what is going on, but I am having trouble finding where to hook up the green wire to the distributor. I have an HEI in my truck, but the whole engine bay is covered in cr*p so I can't really find the place where it hooks in.

Also I read on autozone.com which to me sounds contradictory "Never ground the TACH terminal; serious ignition module and coil damage will result." and just before that it says "Connect one tachometer lead to this terminal and the other lead to a ground." Does that just mean don't connect a wire straight from a terminal to a ground, or no ground at all?

Thanks in advance,
Jared

Oh, this is the tach that I bought. http://www.iequus.com/product_info.p...ory_id=100_120

[beaterC10]

I'm pretty sure the HEI tach terminal is in the cap right next to the power terminal. On my 86 the tach terminal is does not have any connector attached to it.

[SRH916]

The power terminal is the "box like thing" that sticks off the distributor on the drivers side of the truck right?

[jchav62]

Originally Posted by beaterC10

I'm pretty sure the HEI tach terminal is in the cap right next to the power terminal. On my 86 the tach terminal is does not have any connector attached to it.

That's where its at... It's labeled 'tach' right on top...

[SRH916]

I can't see anything in there, and its really hard for me to get to it without crawling in the engine bay. where on the box is this terminal located? Just so I have an idea of where to look.

[jchav62]

On the driver's side of the black coil cover on top of the dist. cap... there's a square piece on the side with wires plugged in from underneath. One is a three-wire plug from the distributor to the cap, one is a single wire plug, and right next to that a vacant one for the tach...

[SRH916]

Ok, Thanks ALOT for that. I couldn't see any other plug, and it was really hard for me to try to get back in there. I'm about 6' and trying to squeeze into the engine bay is quite a tight fit haha I think I can get it now, but can anyone clarify this for me?

Originally Posted by SRH916

Also I read on autozone.com which to me sounds contradictory "Never ground the TACH terminal; serious ignition module and coil damage will result." and just before that it says "Connect one tachometer lead to this terminal and the other lead to a ground." Does that just mean don't connect a wire straight from a terminal to a ground, or no ground at all?

Oh, this is the tach that I bought. http://www.iequus.com/product_info.p...ory_id=100_120

[swb85]

You should have 3 wires coming out of your tach. One goes to a switched 12v source, one goes to ground, and the last one goes to the terminal on the distributor.

[SRH916]

I've got 4 one is for a light switch, one is for a power source +12v, one goes to the tach and another is a ground, but "Never ground the TACH terminal; serious ignition module and coil damage will result." so I'm a little skeptical about using a ground, just because I have no knowledge of electrical systems, and I don't want to fry my distributor.

[Gregs71]

I recently put a tack in my 87. I used the black ground wire and grounded it. My ignition module did go out. I replaced it, and its been fine since. Coincidence, I don't know.

Your tach won't work without the ground, so I am not sure what those directions mean. Possibly a direct ground to the distributor??

Greg

[SRH916]

Thats what I'm afraid of happening. I don't have alot of money for replacing the distributor right now. I'm officially stuck now...

[jchav62]

I think it's just a ground for the tach itself... I think what they mean is never ground the coil directly to the firewall or whatever... It's okay to ground the tach... You'll be fine...

[SRH916]

If anything happens I'm blaming you guys. haha Just kidding. Ok. Well, when I get home. I'll finish up with a hole in the firewall. and get it all wired. I'll follow up just to let you know.

Thanks for all the help I really appreciate it,
Jared

[jchav62]

Good luck! You should have only one wire going through the firewall(to the dist)..the rest can stay inside...I'm sure you'll have no problems....jc

[SRH916]

Finally. It was a PITA to figure out how to get the tach terminal connected. I stuck it in there the first time, and nothing worked :[ and even then the lights all went out... So I fussed with it, and eventually got it into the right terminal (I guess it wasnt a terminal that i had it in the first time)
For anyone elses future reference, the terminal connection is close to the outside of the little "box" if that makes any sense. If you look at it you will understand.

Well anyways, Thank you all for the help.

I really appreciate it,
Jared

[jchav62]

Nice! Glad you got it done...

[blu87]

Related question...
How/where can you run a grounding wire for a hidden ignition cut-off s/w.

[SRH916]

The ground for mine I attached to one of the screws in the door sill. I just wired it under the sill, and screwed it down. Works good. and you can hide it under carpet.

[blu87]

Let me clarify, for security purposes to disable a parked truck, where on the distributor can you attach a gounding wire without frying the module or the coil?

[SRH916]

I read something that says you should never ground your distributor. You will fry it. Maybe someone can come in with a bit more knowledge than me.

[Mickey_D]

You could run the power lead through a relay that was controlled by the ground you're talking about.

Splice into the power lead going to the distributor, put one side of said splice on each of the NC (normally closed) contacts on the relay. Then run an ignition switched jumper from say the heater blower fuse to one side of the relay coil and your grounding switch to the other. Voile'. So long as your ground is active, the relay will be energized. As soon as you break the ground, the relay will de-energize and close the contacts.

The reason I say hook it to something ignition controlled is so that the relay won't be on all the time and run your battery down. You only need it energized when the ignition switch is on anyways so nobody can drive the truck without disabling your mysterious ground, right?