Tach jumps.
Thread Starter
Burning Brakes
Joined: Jun 2008
Posts: 827
Likes: 0
From: Salem Ohio
Tach jumps.
My 78 has a tach that jumps around and when you get barely get on it, the rpm's skyrocket, so im assuming circuit board or what?
Guess I should mention speedo does a little too.......
Guess I should mention speedo does a little too.......
Last edited by shank0668; Nov 22, 2009 at 11:40 AM.
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
Sounds to me like the wire connection at the tach filter might be loose, or not making good connection. Go to the tach filter and check the connection at the distributor, the connection to the harness and also check the wires going in and out of the filter.
I have a new paper on our site about your tach's... You might upload it.. it's free for all to view. http://willcoxcorvette.com/repairand...lp.php?hID=290
Willcox Inc.
In case you don't know where the filter is or what it looks like, here is a picture for you.
I have a new paper on our site about your tach's... You might upload it.. it's free for all to view. http://willcoxcorvette.com/repairand...lp.php?hID=290
Willcox Inc.
In case you don't know where the filter is or what it looks like, here is a picture for you.
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
The bounce in the speedo could be the transducer if you have cruise control, the speedo cable, the the gears in the transmission or the speedo head.
I'd bet the problem is in your cruise transducer and not the speedometer or cables. I think I would start with removing the upper cable at the transducer and run it with a drill. If no bounce you've eliminated the speedo head and if you have bounce remove the speed upper cable and inspect or replace... then do the same test.
If you need to remove the speedometer housing there are instructions on our site at this link. http://willcoxcorvette.com/repairand...lp.php?hID=146
If you are not using the cruise on your car (if you have it) then you can run the longer cable for a car without cruise control which will eliminate the cruise transducer. If you find the transducer is defective, we can rebuild it for you. http://willcoxcorvette.com/product_i...ducts_id=12661
Willcox
I'd bet the problem is in your cruise transducer and not the speedometer or cables. I think I would start with removing the upper cable at the transducer and run it with a drill. If no bounce you've eliminated the speedo head and if you have bounce remove the speed upper cable and inspect or replace... then do the same test.
If you need to remove the speedometer housing there are instructions on our site at this link. http://willcoxcorvette.com/repairand...lp.php?hID=146
If you are not using the cruise on your car (if you have it) then you can run the longer cable for a car without cruise control which will eliminate the cruise transducer. If you find the transducer is defective, we can rebuild it for you. http://willcoxcorvette.com/product_i...ducts_id=12661
Willcox
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
How did the post disappear from this thread? Someone between my post said they also had a problem with the speedo bouncing... Or am I going nuts????
Anyway... No cruise... Then pull the speedo cable off the transmission and run it up with a drill. If you have bounce you've eliminated the gears in the tranny. If it's gone the pull the driven gear out of the tranny and inspect it for damage or missing teeth.
If you run it up with a drill and you still have the bounce, I would replace the cable first and then test again. If you still have the problem, remove the speedo from the car per the instructions above and send it in to us.. We can repair it too if needed.
Willcox Inc.
Anyway... No cruise... Then pull the speedo cable off the transmission and run it up with a drill. If you have bounce you've eliminated the gears in the tranny. If it's gone the pull the driven gear out of the tranny and inspect it for damage or missing teeth.
If you run it up with a drill and you still have the bounce, I would replace the cable first and then test again. If you still have the problem, remove the speedo from the car per the instructions above and send it in to us.. We can repair it too if needed.
Willcox Inc.
Thread Starter
Burning Brakes
Joined: Jun 2008
Posts: 827
Likes: 0
From: Salem Ohio
How did the post disappear from this thread? Someone between my post said they also had a problem with the speedo bouncing... Or am I going nuts????
Anyway... No cruise... Then pull the speedo cable off the transmission and run it up with a drill. If you have bounce you've eliminated the gears in the tranny. If it's gone the pull the driven gear out of the tranny and inspect it for damage or missing teeth.
If you run it up with a drill and you still have the bounce, I would replace the cable first and then test again. If you still have the problem, remove the speedo from the car per the instructions above and send it in to us.. We can repair it too if needed.
Willcox Inc.
Anyway... No cruise... Then pull the speedo cable off the transmission and run it up with a drill. If you have bounce you've eliminated the gears in the tranny. If it's gone the pull the driven gear out of the tranny and inspect it for damage or missing teeth.
If you run it up with a drill and you still have the bounce, I would replace the cable first and then test again. If you still have the problem, remove the speedo from the car per the instructions above and send it in to us.. We can repair it too if needed.
Willcox Inc.
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