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Splitting the tacho signal

2K views 4 replies 2 participants last post by  nitroslick 
#1 ·
Wondered if any one with electrical experience knows how to split the tacho signal wire to two devices .
I have a larger tacho on my bike and also a dynatek shift light ,i can get them both to work by using seperate sources but it would make things neater if they both ran off the tacho signal wire from the ecm .
Any ideas apreciated ,i did try the dynatek tach adapter part 101 but it didnt help.
 
#2 ·
This is my understanding of how the factory tachometer works...

The factory tachometer on our bikes is not an actual tachometer it is just a stepper motor that gets told by the ECM (via the canbus protocol) where to point (it is not a pulse counter) .... the tach signal pin on our ECM is a regular analogue 2 pulse per revolution signal that aftermarket tachs and shift lights recognize internal to the tachometer. So long story short your not going to be able to tie the two together because teh factory tach is expecting a digital signal (Canbus) and the aftermarket tachs are expecting an analogue signal (X number of pulses per revolution)

That being said you can split your analogue tach signal just tie both the aftermarket tach and shift light to the same signal wire.... I am actually running three rpm based devices of my single tach signal (pin 3) currently
 
#3 ·
thanks for replying

Thanks for replying ,i will just have to go with plan b by tapping into the coil signal wires then ,use the ecm pin for the tacho which i already have done and the shift minder on the coils
Could have used an autometer tacho/shift light combined but it was just too big at 5 inch dia
 
#4 ·
You should be able to run both off of the Tach pin, I am doing that now. I have 2 shift lights and a tach all being driven by the ECM pin currently.
 
#5 ·
i did try that by connecting my dynatec shift minder with shift light and a 3 3/4 autometer tacho ,the shift minder powered up but woulnt light at any rpm .
Today i connected it to the coil signal wires using the adapter and it works fine .also tried the tacho adapter off the pin 3 wire but still nno joy.
 
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