76 tach wiring help
Thread Starter
Banned Scam/Spammer
Joined: Jun 2006
Posts: 364
Likes: 3
From: Monroe Washington
76 tach wiring help
Could not get a response in General, so any techs in here??
Anyone have a correct diagram of the tach wiring? I'm trying to correct "BUBBA's" rewire of the engine compartment on my '76 coupe. Issue is the tach is not working. Discovered that the tach filter is missing but when I tried to do a continuity check of the line from the distributor to the connector on the back of the tach, it showed as open. I don't think there is anything in line so I'm thinking the firewall connector is wired wrong. Good thing I have all winter to correct Bubba's masterpiece.
Heres a pic of the firewall connector with the brown tach wire location.
One wiring diagram I have shows the wire should go to location #8, another diagram does not even show a tach wire. All I know is that when I hooked up a multimeter between the distributor end of the wire and the connector on the back of the tach, no continuity.
Anyone have a correct diagram of the tach wiring? I'm trying to correct "BUBBA's" rewire of the engine compartment on my '76 coupe. Issue is the tach is not working. Discovered that the tach filter is missing but when I tried to do a continuity check of the line from the distributor to the connector on the back of the tach, it showed as open. I don't think there is anything in line so I'm thinking the firewall connector is wired wrong. Good thing I have all winter to correct Bubba's masterpiece.
Heres a pic of the firewall connector with the brown tach wire location.
One wiring diagram I have shows the wire should go to location #8, another diagram does not even show a tach wire. All I know is that when I hooked up a multimeter between the distributor end of the wire and the connector on the back of the tach, no continuity.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The wire you are looking at runs straight to the tachometer.
Then on the back of the tach board you should have power and ground...
So first... What is the tach doing when you turn on the ignition? It should go to zero.
If the tach is not going to zero, then pull the connector off the back and with the key on verify the ground, and power. If you have power and ground at the connector and the tach is not going to zero you have a problem in the tach.
If the tach is going to zero, the verify continuity between the connector of the tach wire to the filter all the way to the tach connection. If you have continuity from the back of the tach to the end of the wire where it connects to the filter... You have a board problem.
Willcox
Then on the back of the tach board you should have power and ground...
So first... What is the tach doing when you turn on the ignition? It should go to zero.
If the tach is not going to zero, then pull the connector off the back and with the key on verify the ground, and power. If you have power and ground at the connector and the tach is not going to zero you have a problem in the tach.
If the tach is going to zero, the verify continuity between the connector of the tach wire to the filter all the way to the tach connection. If you have continuity from the back of the tach to the end of the wire where it connects to the filter... You have a board problem.
Willcox
Thread Starter
Banned Scam/Spammer
Joined: Jun 2006
Posts: 364
Likes: 3
From: Monroe Washington
The tach does go to zero when power is applied. My problem is that when I tried to check continuity of the tach wire from the distributor to the back of the tach, no continuity. The wire is good from the distributor to the bulkhead connector, but not past the bulkhead to the tach. I'm thinking that when the engine bay was rewired they connected the tach wire to the wrong position on the bulkhead connector. Two different wiring diagrams showed the tach wire in different locations on the bulkhead connector and the third diagram did not even show a tach wire at all.
I think I am going to run a seperate wire from the distributor to the tach to see if the tach is working, then I'll have to troubleshoot the wiring issue.
Still could use a verified wiring diagram for 1976
I think I am going to run a seperate wire from the distributor to the tach to see if the tach is working, then I'll have to troubleshoot the wiring issue.
Still could use a verified wiring diagram for 1976
Last edited by alyle5864; Oct 20, 2009 at 11:43 PM.
Le Mans Master
Joined: Jan 2007
Posts: 7,819
Likes: 3,200
From: Omaha NE
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2022 C3 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
I just took a look at my brown tach wire, and it's on the same bulkhead connector as yours.....
And I know it's factory.........
And I know it's factory.........
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The tach does go to zero when power is applied. My problem is that when I tried to check continuity of the tach wire from the distributor to the back of the tach, no continuity. The wire is good from the distributor to the bulkhead connector, but not past the bulkhead to the tach. I'm thinking that when the engine bay was rewired they connected the tach wire to the wrong position on the bulkhead connector. Two different wiring diagrams showed the tach wire in different locations on the bulkhead connector and the third diagram did not even show a tach wire at all.
I think I am going to run a seperate wire from the distributor to the tach to see if the tach is working, then I'll have to troubleshoot the wiring issue.
Still could use a verified wiring diagram for 1976
I think I am going to run a seperate wire from the distributor to the tach to see if the tach is working, then I'll have to troubleshoot the wiring issue.
Still could use a verified wiring diagram for 1976
You can run a direct wire for testing! It won't hurt a thing.
I don't have my schematics on this new machine yet... I transferred 50gb of files tonight.
Willcox
Thread Starter
Banned Scam/Spammer
Joined: Jun 2006
Posts: 364
Likes: 3
From: Monroe Washington
Off work today so I ran a direct wire from the distributor to the tach connector on the tach, started engine and tach works. So, it has to be that the wire at the bulkhead connector is off. Guess its back to figuring out the wiring to see where the wire needs to go.
Is it difficult to change the wire connection on the bulkhead fitting???
Is it difficult to change the wire connection on the bulkhead fitting???
Thread Starter
Banned Scam/Spammer
Joined: Jun 2006
Posts: 364
Likes: 3
From: Monroe Washington
Okay, found the problem. Pulled the bulkhead connector and did a continuity check from the tach to the receiver pin and found out the tach wire from distributor was correct but was not making contact with receiver pin on fuse panel side. Reinstalled bulkhead connector and ran continuity check again and solved problem.
New problem. Removed jumper wire from tach, reconnected plug and engine would not start. Pulled tach wire from distributor and engine starts and runs. With engine running connected tach wire and engine stopped. Whats up????? Ground issue maybe??
New problem. Removed jumper wire from tach, reconnected plug and engine would not start. Pulled tach wire from distributor and engine starts and runs. With engine running connected tach wire and engine stopped. Whats up????? Ground issue maybe??
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Thread Starter
Banned Scam/Spammer
Joined: Jun 2006
Posts: 364
Likes: 3
From: Monroe Washington
Well, discovered that the tach wire is shorted to ground!!! Found the problem- the tach wire pin on the bulkhead connector, when the connector is engaged, is shorting against another pin and to ground. Man what a tight fit for your hands.
Thread Starter
Banned Scam/Spammer
Joined: Jun 2006
Posts: 364
Likes: 3
From: Monroe Washington
Problem corrected. Found the contact was crooked in the connector. Reset the contact and got the bulkhead connector back installed with continuity now. Started engine and tach works.
