Tach wire on HEI - Does anything else use this signal?

[Rusty Nail]

So it helped...

Right this second I can't think of ANYTHING else the sometimes present "green tach connector" is intended for other than underhood diagnostics.

I didn't make that up.. It's easy to find that in print elsewhere it is/was taught in A.S.E. classes I clearly recall.

 

[AuroraGirl]

So it helped...

Right this second I can't think of ANYTHING else the sometimes present "green tach connector" is intended for other than underhood diagnostics.

I didn't make that up.. It's easy to find that in print elsewhere it is/was taught in A.S.E. classes I clearly recall.

It's a black wire

You must be registered for see images attach

Well, maybe green but either as a stripe or just so dirty

You must be registered for see images attach

 

[AuroraGirl]

Whoops included a tire from 1980. Can't figure out how to edit on mobile so suck some old tire dick, Mr. Reader

 

[wanderinthru]

Whoops included a tire from 1980. Can't figure out how to edit on mobile so suck some old tire dick, Mr. Reader

That is just not very nice........

 

[wanderinthru]

Tach signal comes from the terminal in the distributor cap next to the power wire.
You'll need a large spade terminal connector and will be forced to wire the tachometer power and ground wires separately.

Hope this helps!

"Forced to wire the tachometer power and ground wires separately" asking for information. Never wired in a tach, though I'm sure I will.

Thanks

 

[AuroraGirl]

"Forced to wire the tachometer power and ground wires separately" asking for information. Never wired in a tach, though I'm sure I will.

Thanks

i didnt notice that, but damn.

sure hope i know to wire the power and ground separate!

 

[wanderinthru]

"Forced to wire the tachometer power and ground wires separately" asking for information. Never wired in a tach, though I'm sure I will.

Thanks

Baahahahahahaha, didn't get that last night. ****** typed sarcasm!!! But ya got me Rusty...

 

[Rusty Nail]

Whatever.

 

[semperfiguy98]

For what it's worth..
There is another function of the tach lead coming out of the HEI distributor cap. My 86 K20 Suburban(California emissions) has a wire coming out of the tach lead on the cap. I don't have a tach. The wire goes to a metal box (kinda looks like an old horn relay) on my driver side valve cover. That controls a solenoid on the driver side front of the carb, kinda like the solenoids that increase RPM when AC is turned on. In the case of my truck it's used to slow down the closing of the throttle when you're at highway speeds and suddenly let off the gas. I found the description of how it works in the service manual. I've only ever seen this on CA trucks, but could be on others as well.

 

[DoubleDingo]

im asking for my buick but it does apply in general to HEI. even without a tachometer, what might it go to?

Maybe if you wanted a sick thrill and wired it to a nipple ring or nose ring, you could get zapped a few thousand times a minute

 

[Rusty Nail]

Pix?

 

[AuroraGirl]

For what it's worth..
There is another function of the tach lead coming out of the HEI distributor cap. My 86 K20 Suburban(California emissions) has a wire coming out of the tach lead on the cap. I don't have a tach. The wire goes to a metal box (kinda looks like an old horn relay) on my driver side valve cover. That controls a solenoid on the driver side front of the carb, kinda like the solenoids that increase RPM when AC is turned on. In the case of my truck it's used to slow down the closing of the throttle when you're at highway speeds and suddenly let off the gas. I found the description of how it works in the service manual. I've only ever seen this on CA trucks, but could be on others as well.

Awesome thanks for the input. I should make sure mine doesn't have anything like that.

 

[SirRobyn0]

im asking for my buick but it does apply in general to HEI. even without a tachometer, what might it go to?

I'm going to preface this by saying I did not read though all of the posts. To my knowledge the tach wire on a GM HEI ignition is only used for a tach, or in the 80's when they started computerizing carbed engines sometimes the computer would use the tach signal. I seem to think I can remember a few using the tach signal the heat wire for the choke on some cars, but in your picture it doesn't look like an electric choke, so I'm really not sure. If it were me I'd disconnect the wire see if it'll fire up and if anything doesn't work right with it disconnected.

 

[AuroraGirl]

I'm going to preface this by saying I did not read though all of the posts. To my knowledge the tach wire on a GM HEI ignition is only used for a tach, or in the 80's when they started computerizing carbed engines sometimes the computer would use the tach signal. I seem to think I can remember a few using the tach signal the heat wire for the choke on some cars, but in your picture it doesn't look like an electric choke, so I'm really not sure. If it were me I'd disconnect the wire see if it'll fire up and if anything doesn't work right with it disconnected.

I got the 77 buick full size manual and confirmed it's just a diagnostic wire. As in, it takes the tach signal and moves it 2 feet to be readable on the fender instead of the cap. In this specific instances, at least.

 

[SirRobyn0]

I got the 77 buick full size manual and confirmed it's just a diagnostic wire. As in, it takes the tach signal and moves it 2 feet to be readable on the fender instead of the cap. In this specific instances, at least.

Good to know.