Tachometer problems...
Thread Starter
Obsessed
Joined: Apr 2019
Posts: 627
Likes: 394
From: Valencia, Spain
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2019 C3 of Year Finalist (stock)
Tachometer problems...
All of the sudden I started getting erratic jumping around on my tachometer although the engine runs smooth. Checked the tach cable connections in the engine bay. It has a short extension cable that’s connected to the distributor. Then that connects to the cable that enters the firewall going to the tach. I haven’t been able to check the cable connection at the tachometer. Weird observation, the tachometer works fine when the engine is cold.., Once it’s warmed up the tach starts going erratic or just drops to 0... Any ideas???
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,116
Likes: 9,247
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
you may have a broken tachometer cable, I just broke mine today.....but mine stays at zero...
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,008
Likes: 4,166
From: US-PNW
Perhaps you lost the link and connection to the last time you pursued this:
https://www.corvetteforum.com/forums...see-video.html
I replied this, did you get a chance to check it?
I'd be really curious to investigate this two-part tach cable arrangement.
https://www.corvetteforum.com/forums...see-video.html
I replied this, did you get a chance to check it?
That's odd. I know the speedometer cable can be a two-part assembly but never heard of the tach cable being that way.
Before tearing into your dash, disconnect the tach cable at the distributor. You should be able to spin it by hand and not feel any binding. If you do feel something, disconnect the cable junction you mentioned above and try it with the cable section coming from the firewall. You could test the tachometer itself by spinning the cable with a drill. I don't recall the necessary direction, so use a reversible drill. Make sure the needle isn't bouncing around when the drill is at a steady speed.
Before tearing into your dash, disconnect the tach cable at the distributor. You should be able to spin it by hand and not feel any binding. If you do feel something, disconnect the cable junction you mentioned above and try it with the cable section coming from the firewall. You could test the tachometer itself by spinning the cable with a drill. I don't recall the necessary direction, so use a reversible drill. Make sure the needle isn't bouncing around when the drill is at a steady speed.
Last edited by barkingrats; Jun 20, 2020 at 09:41 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
I would suspect a problem with the connection between the two cables. The ends of the cables are 1/8" square drive. If the frays or wears, it will drive no more.....even though it is spinning. The tach head has a worm gear which might be worn out. I would try the cables first, before digging into the "pit of DOOM" behind the dash pad....
