Tach wire/distributor...LOST! eeks!
Thread Starter
Pro
Joined: Oct 2006
Posts: 545
Likes: 2
From: Peoplez Republik (communist portland) Orygun
Tach wire/distributor...LOST! eeks!
On my 1980 350, I have been without use of tach for 6 months. The tach needle flacidly sits at 6000 & doesn't move at all. Dead...So, I finally decided to figure it out...But wait...After scouring over the 1980 build book & owners manuals, numerous publications & pictures, I am still stumped.
What wire goes here? Is this why I have no tach? If you have HEI, do you have a wire that goes to this?
Does this wire lead go to it? Or anywhere? (orange wire w/ brown cap)
Does anything snap in there? I can't find anything. Your knowledge & brainpower I humbly seek.
Yes, it looks simple right? well dummy, plug that orange wire (with brown cap) into the spot marked TACH on the coil cover right? Not so easy, that little wire is ablout 2 inches too short to reach the fitting on the distributor. Plus, as you know with HEI, it's MUCH better to be safe than sorry by blindly plugging hot leads into open sockets.
-Tachless in Portland
What wire goes here? Is this why I have no tach? If you have HEI, do you have a wire that goes to this?
Does this wire lead go to it? Or anywhere? (orange wire w/ brown cap)
Does anything snap in there? I can't find anything. Your knowledge & brainpower I humbly seek.
Yes, it looks simple right? well dummy, plug that orange wire (with brown cap) into the spot marked TACH on the coil cover right? Not so easy, that little wire is ablout 2 inches too short to reach the fitting on the distributor. Plus, as you know with HEI, it's MUCH better to be safe than sorry by blindly plugging hot leads into open sockets.
-Tachless in Portland
Last edited by Vette80regon; Jan 7, 2007 at 12:27 PM.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
You have a spot of luck, and have been driving without a tach needlessly. According to my working HEI tach, and the color of wires I have...all you have to do is plug in the brown wire and you're good. But, I cannot see where it originates. It should come from the same place as the red wire. If it's not...trace it and find it's source and test it with ignition on.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
The tac wire should be white, with a silver canister at one end. This is the tach "filter", and should be mounted to a good ground. Your "orange " wire may be it, as these sometimes fade and look different.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
You have a spot of luck, and have been driving without a tach needlessly. According to my working HEI tach, and the color of wires I have...all you have to do is plug in the brown wire and you're good. But, I cannot see where it originates. It should come from the same place as the red wire. If it's not...trace it and find it's source and test it with ignition on.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I know, but he has to trace that brown wire. If it does not go back to the tach than hooking it up, short or not, will not help him. He may have to crawl on his back, and find the correct tach wire and run it through the firewall if that brown wire is not it.
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
There should be a wire on the distributor plug marked "tach". I have my motor out of the car right now so I'm not sure what wire goes there. I'm sure that someone here will be able to help you out. Good luck.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
The brown wire and plug from my pic is what was plugged into the tach spot. But as I said, if that brown wire doesn't go to the tach than it's not gonna do anything. I think a 12V source into that wire should make the tach jump...but that's just something I heard.
Thread Starter
Pro
Joined: Oct 2006
Posts: 545
Likes: 2
From: Peoplez Republik (communist portland) Orygun
Thanks gang, I'm gonna jack 'er up and roll under the car & trace it all out before I connect it. If I can't find the location point (ie...bundles up to the wiring harness), I'll just go for broke & plug in the "Orange" wire into the TACH socket on the distributor & hope for positive results..."ZZZZsssshpppt!" If my wife hears that sound and me shriek "OUCH!!!!" Then we'll know it didn't work.
Wish me luck, I'm going in!
Wish me luck, I'm going in!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
c- = tach signal, it even says so on the cap. The wire should indeed be white. Is yours a 305 LG4 calif emissions car? If so, and the tan wire has a black stripe then that's the hei bypass..if that's the case, connect it since the EST will be bypassed and you will run @ base timing.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
The tach signal is a "pulse" signal less than 5 volts. 12 volt will fry the board.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Thread Starter
Pro
Joined: Oct 2006
Posts: 545
Likes: 2
From: Peoplez Republik (communist portland) Orygun
I hooked it up (fire extinguisher nearby
) then fired the car up. It must be the correct wire as the tach needle jumped to life when it started. It pulsed with the engine correctly for about 5 seconds. Sadly & Unfortunately it spun itself off the charts and is eternally driving at what I would guess 14,000 RPM (sarcasm for being buried totally clockwise). After a 10 minute joy ride around the neighborhood I shut the car off and it still is buried, hasn't budged.
Now...Could it be the circuit board? Has this ever happened to you?
To access the circuit board I have to remove the dash/bezel correct?
Thanks for all the input this morning!
) then fired the car up. It must be the correct wire as the tach needle jumped to life when it started. It pulsed with the engine correctly for about 5 seconds. Sadly & Unfortunately it spun itself off the charts and is eternally driving at what I would guess 14,000 RPM (sarcasm for being buried totally clockwise). After a 10 minute joy ride around the neighborhood I shut the car off and it still is buried, hasn't budged. Now...Could it be the circuit board? Has this ever happened to you?
To access the circuit board I have to remove the dash/bezel correct?
Thanks for all the input this morning!
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Did you extend that brown wire?
Did you trace it to see where it came from?
If is wasn't a tach wire and harmed it...I wonder what you hooked up.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
I hooked it up (fire extinguisher nearby ) then fired the car up. It must be the correct wire as the tach needle jumped to life when it started. It pulsed with the engine correctly for about 5 seconds. Sadly & Unfortunately it spun itself off the charts and is eternally driving at what I would guess 14,000 RPM (sarcasm for being buried totally clockwise). After a 10 minute joy ride around the neighborhood I shut the car off and it still is buried, hasn't budged.
Now...Could it be the circuit board? Has this ever happened to you?
To access the circuit board I have to remove the dash/bezel correct?
Thanks for all the input this morning!
) then fired the car up. It must be the correct wire as the tach needle jumped to life when it started. It pulsed with the engine correctly for about 5 seconds. Sadly & Unfortunately it spun itself off the charts and is eternally driving at what I would guess 14,000 RPM (sarcasm for being buried totally clockwise). After a 10 minute joy ride around the neighborhood I shut the car off and it still is buried, hasn't budged. Now...Could it be the circuit board? Has this ever happened to you?
To access the circuit board I have to remove the dash/bezel correct?
Thanks for all the input this morning!
You need to trace that wire and see what Bubba did about that filter.
You will probably need to pull the tach, unstick the needle, and replace the circuit board.
There may be a tech paper on this, but I don't know. Good luck
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Boy no one wants to hear that.
Drifting
Joined: Jan 2005
Posts: 1,438
Likes: 3
From: Florissant MO
This will give you a little info on what is involved in circuit board replacement.
http://www.corvettemagazine.com/2006...meter_tach.asp
My tach stopped working the other day. Found out that the filter was getting 12v from the distributor and 12v on the other side of the filter which fried the board. Now I have to get a new filter and a new circuit board.
Waiting for warmer weather now.
http://www.corvettemagazine.com/2006...meter_tach.asp
My tach stopped working the other day. Found out that the filter was getting 12v from the distributor and 12v on the other side of the filter which fried the board. Now I have to get a new filter and a new circuit board.
Waiting for warmer weather now.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
This will give you a little info on what is involved in circuit board replacement.
http://www.corvettemagazine.com/2006...meter_tach.asp
My tach stopped working the other day. Found out that the filter was getting 12v from the distributor and 12v on the other side of the filter which fried the board. Now I have to get a new filter and a new circuit board.
Waiting for warmer weather now.
http://www.corvettemagazine.com/2006...meter_tach.asp
My tach stopped working the other day. Found out that the filter was getting 12v from the distributor and 12v on the other side of the filter which fried the board. Now I have to get a new filter and a new circuit board.
Waiting for warmer weather now.