elec tach problem
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 923
Likes: 4
From: Austin Tx
elec tach problem
I replaced my mech tach in my 72 with a used elect tach from a 75, using a homemade tach filter from another forum member who was nice enough to send one to me. Above 2500 rpm, the dam thing bounces and spikes all over the place, then above 3500 it gets really bad, bouncing ahead to 5500 rpm. What fixes this assuming all my connections are good?
Le Mans Master
Joined: Jan 2001
Posts: 6,742
Likes: 1,384
I'd make a new tach filter....
first. It's only like a dollar or two in parts from Radio Shack. If that doesn't work, then I'd buy a new circuit board.
I had to put an electric tach in my 68 and I had to do both. I'm still glad to be rid of that mechanical tach.
I had to put an electric tach in my 68 and I had to do both. I'm still glad to be rid of that mechanical tach.
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 923
Likes: 4
From: Austin Tx
Sounds great except I don't have the skills to build a tach filter myself. Will just buy one from one of the vendors and probably also buy a new board too since I will have to remove the damn dash again...
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 923
Likes: 4
From: Austin Tx
Originally Posted by Gage
I'm going to bypass the tach filter and see if that makes a difference.
Bypassed the filter, no more needle bounce or spiking...guess that was my problem.
Pro
Joined: Nov 2004
Posts: 659
Likes: 0
From: Flower Mound Texas
Hmm. Interesting. A couple of years ago when I was troubleshooting the tach on my 75, there was a poster on this forum that cautioned everyone about running without a filter. He claimed running without a filter shortened the life of the tach circuit board. Interestingly, my circuit board was burned up and there was no filter when I bought the car.
Burn a 20-spot on a non OEM filter:
http://www.rodneydickman.com/CorvetteTachFilter.html
Burn a 20-spot on a non OEM filter:
http://www.rodneydickman.com/CorvetteTachFilter.html
