Tach bobble

[BlueRooster]

Last night I went for a nice long drive. Last week I installed the
Optima 34 (red top)and all went well. She seems to start better cold
and hot. While driving last night though, I noticed the tach bobbing
up and down...kept looking and it would just die and then come back
to life. By the time I got back home, this seemed to disappear. No
other gauge had this problem and the car ran great otherwise. Do you
think it is the tach itself? Or a wire? The new battery? Anyone
else experience this?

[scottj]

Yes. What is it? Tach is a S-W. Never had a problem before.

[Cobra20646]

My gut feeling is you have a wire loose. Check from the coil/ignition box (tach feed) all the way to the back of the tach. Also make sure the 12 volts feeding the tach is good and tight too.
Could be the tach, but check the wiring thoroughly first.

- Jim -

PS..... Smiths tach? all bets are off

[BlueRooster]

It is a Smiths.....every day they work is a blessing.

[Mr.Fixit]

Smith's tach's don't have the same failure rateas their other gauges,I have never replaced asmith's tach, but dozens of their temp and pressure gauges. I am betting on a poor connection, a lot of guys just use those clamp-over-wire jumper connections for the tach wire, not good. Do you have an MSD box? If so, it could possibly be your tach adapter or inline capacitor, if you have those. Bad tach is possible, but I would rule out the other possibilities first.

[John Poling]

Make sure you have clean bare metal - sealed ground connections. Ground faults are the highest failure items in electrical systems bar none.

John

[edwhite7]

If you have a dual point dist. it could be the dwell. My smith tach would die on me if the dwell was not perfect. I converted to an MSD box with MSD dist. and the tach has worked fine ever since.