Ruano1987 Posted February 4, 2015 Report Share Posted February 4, 2015 For the past couple days when I'm driving on the freeway and I am in 4th maintaining 55mph my tach needle starts freaking out bouncing anywhere from 3k to 6k then back then 4k to 7k etc. When I'm driving in town I have no issue just on the freeway and this morning it felt laggy when the tach was bouncing. Any help will be appreciated 1 Quote Link to comment
harlow426@mail.com Posted February 4, 2015 Report Share Posted February 4, 2015 I'll bet there is/are contaminates under the dist cap or cap/rotor worn(air gap too great). If u buy new ones get OEM grade parts with brass terminals. Aluminum contacts/terms are NOT oem grade......false advert/packaging. Wear out fast....inferior conductivity. Aluminum BAD!! If you disconnect the tach wire it won't bounce. Air gap between hall sender/reluctor inside dist could b wrong as well. 2 Quote Link to comment
Ruano1987 Posted February 4, 2015 Author Report Share Posted February 4, 2015 I purchased oem parts from my local nissan dealer. This issue started right after I rebuilt my carb 2 Quote Link to comment
kelowg Posted February 4, 2015 Report Share Posted February 4, 2015 Loose wires/grounds 2 Quote Link to comment
Gradyfest Posted February 11, 2015 Report Share Posted February 11, 2015 Did you ever figure this out? Mine has done the same thing since the day I bought it... Quote Link to comment
datzenmike Posted February 11, 2015 Report Share Posted February 11, 2015 The tach signal is taken from the + (edit) side of the coil and nothing on the secondary side will affect operation including the dizzy cap or high tension wires/plugs. I wouild make sure that there is no loose wires on the coil + or - side. Find the in line resistor on the harness between the coils and the driver's side headlamps... maybe loose/bad connection 2 Quote Link to comment
that-son Posted February 18, 2015 Report Share Posted February 18, 2015 i always thought it was a vacuum leak that did this until i replaced all vac lines and plugged all the leaks. Quote Link to comment
petercscherer Posted February 18, 2015 Report Share Posted February 18, 2015 i always thought it was a vacuum leak that did this until i replaced all vac lines and plugged all the leaks. Vacuum would have no theoretical effect on Tachometer operation since the tach is electronic and simply reads the rhythm of the coil signals. Vacuum leaks would cause real changes in RPM, but the OP would have also felt MAJOR changes in power, speed, and engine operation; not just seen the needle bouncing alot. Quote Link to comment
datzenmike Posted February 20, 2015 Report Share Posted February 20, 2015 When the tach on my '70 Dart started bouncing I knew it was time to replace the points. Anything that interrupts the on and off pulses to the coil will be read by the tach 3 Quote Link to comment
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