Eractic tach problem
Thread Starter
Racer
Joined: Mar 2005
Posts: 471
Likes: 1
From: Hometown The best
Eractic tach problem
When the tach on my '79 reachs about 4500 rpm it drops to zero and won't work at all for a while, then it will start working again. Sometimes I'm postive that it is not accurate. At idle which is nomally set at 750 the tach shows anywhere from 200 to 500 and when I'm pushing it a little the tach shows 3500 to 4000 but the engine sounds like it turning 5000 to 5500. Any body have an idea why this is happening and how to correct it. Thanks
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Bypass the filter at the dist and see if that helps. If it doesnt ,go to the Willcox site in the help section for tach's.
edit- here you go,down at the bottom
http://willcoxcorvette.com/advanced_...tach&x=39&y=15
edit- here you go,down at the bottom
http://willcoxcorvette.com/advanced_...tach&x=39&y=15
Last edited by ...Roger...; May 15, 2011 at 10:52 PM.
Advanced
Joined: Aug 2011
Posts: 71
Likes: 1
From: Coshocton Ohio
tach doesn't zero with engine off
Dumb question, guys! Ready? How come when I kill the engine on my '78, the tach doesn't fall to zero? Turn the key back on without starting the engine and it drops to zero, but then climbs back to 200 or so. Turn the key off right then and it stays at 200 or so. Not a home wrecker, but a curiosity at least. Thoughts? Thanks!
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Dumb question, guys! Ready? How come when I kill the engine on my '78, the tach doesn't fall to zero? Turn the key back on without starting the engine and it drops to zero, but then climbs back to 200 or so. Turn the key off right then and it stays at 200 or so. Not a home wrecker, but a curiosity at least. Thoughts? Thanks!
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
When the tach on my '79 reachs about 4500 rpm it drops to zero and won't work at all for a while, then it will start working again. Sometimes I'm postive that it is not accurate. At idle which is nomally set at 750 the tach shows anywhere from 200 to 500 and when I'm pushing it a little the tach shows 3500 to 4000 but the engine sounds like it turning 5000 to 5500. Any body have an idea why this is happening and how to correct it. Thanks
Here is the tach filter:
Here are instruction sheets and diagnostic pages that will help you!
http://willcoxcorvette.com/advanced_...s=tach&x=0&y=0
At the bottom of the page you'll see "Repair help"... just select the topic and then click on supporting document.
Willcox
Racer
Joined: May 2011
Posts: 373
Likes: 6
From: Dover Delaware
erratic tach.............
Had the same problems with my 78 tach..had my vette man troubleshoot it and he said it needed to be rebuilt. He sent it out and had a new circuit board installed and had it calibrated, he reinstalled it and it works great.....a little pricey but when ya think about trying to do it all yourself and then not having any calibration tool to finish the rebuild..well you know how that story goes................
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Had the same problems with my 78 tach..had my vette man troubleshoot it and he said it needed to be rebuilt. He sent it out and had a new circuit board installed and had it calibrated, he reinstalled it and it works great.....a little pricey but when ya think about trying to do it all yourself and then not having any calibration tool to finish the rebuild..well you know how that story goes................
We have a service offer till the end of this year:
If you purchase our board and mail in the tach.. we'll match calibrate it for 15.00 provided you pay the return shipping! The board is 58.00 so that makes the total 73.00 plus shipping.
Willcox
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Racer
Joined: May 2011
Posts: 373
Likes: 6
From: Dover Delaware
A little pricey??? He must have sent it else where..
We have a service offer till the end of this year:
If you purchase our board and mail in the tach.. we'll match calibrate it for 15.00 provided you pay the return shipping! The board is 58.00 so that makes the total 73.00 plus shipping.
Willcox
We have a service offer till the end of this year:
If you purchase our board and mail in the tach.. we'll match calibrate it for 15.00 provided you pay the return shipping! The board is 58.00 so that makes the total 73.00 plus shipping.
Willcox
But thanks for your input....perhaps I'll think about you for a turn around repair part that I am sure I can get off and on without taking the vette apart.
Thanks,
mk's78
