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tach bounce

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jvandyke

jvandyke

Luke Skywalker
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My tach always was a bit bouncy before and after the conversion to negative earth, in the last few days it has gotten really bad, swinging wildly then settling down until revs change then it swings away again. What causes this and can I do anything about it? (I'm about to try to install an XR700 and that might not help?).
 
Try grounding the tach with a new ground wire from a screw on the housing that holds the guts to a good ground.
They are normally grounded via the thumb screw on the back, another fresh ground usually helps.
 
Great, will do and report back.
 
I simply wiggled and tightened the existing ground and it was back to where it was: a little bounce. Makes me wonder if I ran a new better ground (all rewired this winter so it can't be too bad) would it get better yet?
Thanks!!
 
The grounds on the instruments are really bad. Doesn't matter so much if it's just for a light bulb, but it can affect the electronics and make strange things happen. So, yes, run a good solid ground from the case to the chassis and see what happens. Of course, make sure all other connections are solid.

If that doesn't fix it, it could be in the tach electronics or the meter movement itself.
 
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