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

[AuroraGirl]

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

 

[82sbshortbed]

Nope, just for tach use as far as I know

 

[AuroraGirl]

This damn car was rigged together so much to get it sold to me. had a damn engine fire that i now determine is due to fuel vapor shooting at hot parts on the rear of the engine and melting vacc hoses made from pens and other improper sticks. emissions components were taped off with tape, etc.Surprised it ran. the cap might just have a tach lead attached.. ill see if it goes aanywhere. its a mess.

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[Vbb199]

What year is that buick??

I assume since it's got a carb fuel injection is out of the question.
I was gonna say tach signal would be needed for ECM.... But... Looks like there is no ECM.

 

[AuroraGirl]

There is no ECM. There is a brake and AC diagnostic port. so they have computers of some kind
1977, the year of our lord.

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[AuroraGirl]

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[Vbb199]

OK, wasn't really sure what buick we were talking about. You have like, 100 buicks.


Then yes, the signal wire is just used for a tach.

 

[Matt69olds]

That orange terminal block was GM first attempt at a diagnostic connector. I have seen many cars around the same age with the same connector mounted in various places under the hood.


The tech terminal is mainly used for a tach connection. I have seen aftermarket cruise control setups that have a tach input.

Some of the things previous owners do baffle me. A Mickey Mouse repair made at the side of the road just to get home? Ok, I can definitely understand that. If it’s really stupid in a creative way, I might even congratulate you for a McGuyver worthy fix. However, the people who spend more time and money trying to half-ass thing than just fixing it the correct way really grind my gears!! Even more so when the temporary fix becomes permanent.

 

[75Monza]

You found grandma's LeSaber, lol. Can't think of anything other than tach that it can be used for either. Not sure I'd run it very far, isn't that the temp sensor with no wiring and open hole for PVC with hose going elsewhere from carb?

 

[AuroraGirl]

You found grandma's LeSaber, lol. Can't think of anything other than tach that it can be used for either. Not sure I'd run it very far, isn't that the temp sensor with no wiring and open hole for PVC with hose going elsewhere from carb?

Electra. and yes to your questions..

That orange terminal block was GM first attempt at a diagnostic connector. I have seen many cars around the same age with the same connector mounted in various places under the hood.


The tech terminal is mainly used for a tach connection. I have seen aftermarket cruise control setups that have a tach input.

Some of the things previous owners do baffle me. A Mickey Mouse repair made at the side of the road just to get home? Ok, I can definitely understand that. If it’s really stupid in a creative way, I might even congratulate you for a McGuyver worthy fix. However, the people who spend more time and money trying to half-ass thing than just fixing it the correct way really grind my gears!! Even more so when the temporary fix becomes permanent.

based on observations and following known wires, ive determined the diagnostic connector is not a connector. its a dedicated circuit testing block. Basically, the power of any circuit routes there to be read by a multimeter, its use assuredly depends on the values and pinout in the 77 buick manual, to be sure.

im going to be getting one but thought that was.... obnoxious. the tach wire literally just moves the location of the signal from the cap to the fender, essentially. no communication between things other than warning lights on dash for brake/ac stuff, which prob dont work anyway

 

[75Monza]

My favorite boat I picked up for free was a '67 Electra 225 4 door HT with a 430 big block. Hauled it away for free, spent $200 getting it running, brakes and tires. Car just floated down the road, loved that beast!

 

[Matt69olds]

I stand corrected. It’s been a LONG time since I have seen a car with that connector, and even longer since I worked on one. I assumed the dealerships had a primitive scanner to would plug into the connector. Other than having all the wires in one location, I fail to see a benefit of back probing a terminal.

 

[AuroraGirl]

I stand corrected. It’s been a LONG time since I have seen a car with that connector, and even longer since I worked on one. I assumed the dealerships had a primitive scanner to would plug into the connector. Other than having all the wires in one location, I fail to see a benefit of back probing a terminal.

some are hard to find. and it may very well have had a breakout box kinda deal like ford, idiot lights to tell if circuit is working right. im just saying its essentially just access point for all the wires

 

[Rusty Nail]

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!

 

[AuroraGirl]

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!

I didn't need help setting a tach up lol , silly.
I was tryna identify the use of the tach signal in a car without a tach, and I've determined it's only function is to provide the signal 2 feet to the right for diagnostic assistance