Jumping tach needle
Thread Starter
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Jumping tach needle
I was going down the freeway at 70 mph a few minutes ago, and I noticed the tach was at 3400 instead of 3200. Then suddenly it went back to normal. And it jumped up once, then it was OK.
This is an stock HEI ignition system with a regular tach. I'm guessing either ignition module or tachometer electronics (sticky needle maybe?).
Any guesses? :smash:
This is an stock HEI ignition system with a regular tach. I'm guessing either ignition module or tachometer electronics (sticky needle maybe?).
Any guesses? :smash:
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Jumping tach needle (page62)
My needle was rather bouncy, then it stuck at ~2500. Cable was hitting a stop inside the distributor gear/tach drive. I tested with power hand drill (needs to be run in reverse) to check. As I pushed in on the cable with drill, it either didn't register, or bounced. Tach now reads very steady, not bouncing way past rev point as it did.
Chuck
Just reread your post and see that you have electric tach. Never mind! :bb
Chuck
Just reread your post and see that you have electric tach. Never mind! :bb
Pro
Joined: Mar 2001
Posts: 633
Likes: 1
From: Hamilton, ON, Canada
Re: Jumping tach needle (page62)
Sounds like incipient Tach failure. Mine behaved the same way-erratic behaviour with no pattern. When I replaced the Tach, everything was fine. That was about 17 yrs ago. I understand that replacement Tachs are no longer available but replacement cards are.
Melting Slicks
Joined: Aug 2001
Posts: 2,753
Likes: 1
From: Fishkill NY
Re: Jumping tach needle (page62)
Mine jumps around (about 200 to 300 rpm) when I get to around 4500rpm. Its electronic so, not sure what that would be.. Never gave it much thought but, I saw this post..
Le Mans Master
Joined: Jan 2001
Posts: 9,248
Likes: 221
From: Dryden MI
Re: Jumping tach needle (bud snyder)
On my 80, my tach was extremely erratic, bounced all over constantly. It wound up being the alternater. Sounds weird, but it fixed my tach bounce. The alternater was over charging. Roger L. Gibbbons
Instructor
Joined: Jan 2000
Posts: 163
Likes: 0
From: Fullerton CA
Re: Jumping tach needle (page62)
Page62,
Had similar problem on my '80. After sustained high speed driving, my tachometer would consistently indicate 300-500 RPM high. Pulled the tach and replaced the circuit board (available from any of the parts magazines). This fixed the problem immediately. Good chance to replace the light bulbs too.
Good Luck,
Tom
Had similar problem on my '80. After sustained high speed driving, my tachometer would consistently indicate 300-500 RPM high. Pulled the tach and replaced the circuit board (available from any of the parts magazines). This fixed the problem immediately. Good chance to replace the light bulbs too.
Good Luck,
Tom
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
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
