Dead speedo/crazy tach
Thread Starter
Burning Brakes
Joined: Apr 2004
Posts: 814
Likes: 2
From: WESTLAKE LA
Dead speedo/crazy tach
After setting for 12 yrs, got car going again 
speedometer does not work and tach has decided to stay around 4000 rpms if engine is on.where do i start looking?
speedometer does not work and tach has decided to stay around 4000 rpms if engine is on.where do i start looking?
I have your same problem 
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
The speedometer is gear driven and shouldn't be too hard of a fix...while you're at it, you can get a 140 mph from redline for about $60.00...way better than the 85 mph, if that's what you still have....
The tach is all electronic....you're screwed..
BTW, I've got a brand new, in the box Helm shop manual with electrical diagrams, if you're interested...
The tach is all electronic....you're screwed..
BTW, I've got a brand new, in the box Helm shop manual with electrical diagrams, if you're interested...
Burning Brakes
Joined: Dec 2003
Posts: 782
Likes: 0
From: Elizabeth New Jersey
Originally Posted by Avette4me
The tach is all electronic....you're screwed..
Old cars are so much easier to fix
I had a dead tach in my 89 firebird before I got the vette, it was electric which used a VSS ( vechile speed sensor ) box.
The problem could be a few things if its electrical, could be the VSS usually a yellow box on pass side in firebirds, should be same place in vettes too, not sure mine is cable driven.
Or it could just be a bad guage cluster head, but doubt.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
The VSS is the vehicle speed sensor and has nothing to do with the tachometer, only w/ fuel injection or a lockup on a 350C. The yellow box is not the complete VSS, there's an optical sensor/sender combo in the back of the speedo, one shines and the other one registers the pulses frm the light being bounced back by the mirror thing on the back of the speedo (looks like a flat propellor thing spinning around)
The speedo is cable driven so there's only 2 cables to check if you have a cruise transducer, check the driven & drive gear & cables and check the transducer and the back of the speedo.
As for the tach, probably the circuit board on the back.
The speedo is cable driven so there's only 2 cables to check if you have a cruise transducer, check the driven & drive gear & cables and check the transducer and the back of the speedo.
As for the tach, probably the circuit board on the back.
Last edited by Twin_Turbo; Aug 18, 2004 at 02:07 PM.
