EDIS Tach Signal - Combine Negative Coil Signals

[TrumpetRhapsody]

Yeah I tried the IDM signal from edis to no avail. Next step would be to try the MS output.

[Six_Shooter]

Just bypass the resistor.

 

If the output from the EDIS didn't work, the output from the MS likely won't either.

[Xnke]

hmmm. You're positive this is a voltage sensing tach? if so, the like others are saying, bypass the resistor and pull your signal from MS or EDIS first, then try the diodes. That input resistor might be swamping the tach signal.

 

As for pulling the tach, there is a bracket behind the dash that holds it in place, unscrew the nuts that hold the bracket in and it should pull out. I don't think it comes out through the front, so your dash cap shouldn't be an issue.

[TrumpetRhapsody]

If i can get the tach out the back of the dash I'll try that first with the combined diodes, then try the MS tacho output.

[Six_Shooter]

Tach, comes out the front.

[TrumpetRhapsody]

I've been updating over in this thread: http://forums.hybridz.org/index.php/topic/73574-tach-with-edis-and-msii/page__view__findpost__p__926272

 

I've tried a 12v pullup, with or without the zener connected, with or without the 2.2k resistor inline, adding more resistors, I even dug the tach out the back of the dash and did the resistor bypass mod Six_shooter was talking about, to no avail.

 

My tach only wants to work when I hold the wires a couple millimeters apart in my fingers, as soon as you touch the wires together it dies.

 

 

Any last words before I throw in the towel and buy a real tach? My troubleshooting patience only goes so far, and I'd say 2 years is stretching it.

Edited March 10, 2011 by TrumpetRhapsody

[lowrider]

I've been updating over in this thread: http://forums.hybridz.org/index.php/topic/73574-tach-with-edis-and-msii/page__view__findpost__p__926272

 

I've tried a 12v pullup, with or without the zener connected, with or without the 2.2k resistor inline, adding more resistors, I even dug the tach out the back of the dash and did the resistor bypass mod Six_shooter was talking about, to no avail.

 

My tach only wants to work when I hold the wires a couple millimeters apart in my fingers, as soon as you touch the wires together it dies.

 

 

Any last words before I throw in the towel and buy a real tach? My troubleshooting patience only goes so far, and I'd say 2 years is stretching it.

I'm pretty sure you would still have the same problem with a "real tach". When I was trouble-shooting mine, I took my spare sunpro mini tach and attached it to the factory wiring via an old tach plug. It was unreponsive when the wires were connected. It worked when you held them apart in your fingers, just like the stock piece. I think its more of a signal thing. Like I said in the other thread, i eventually found some combination of components that finally made it work.

[TrumpetRhapsody]

Wow Ok... time for a slice of humble pie. Apparently two years ago when I was troubleshooting this issue, I soldered everything back together with the Zener diode facing the wrong way (didn't work in either direction though). So what this tells me is that with the proper circuit out of the megamanual (apparently the 12v zener is ok), and by bypassing the internal resistor, this WILL work. My Z is outside running, with the tach reading. I rev'd it out to 6500rpm (or so it said) and it doesn't drop, looks smooth. From here I'll start seeing how accurate it is compared to logs.

 

Thanks for the help everyone.

[TrumpetRhapsody]

Just wanted to update this thread to say that the 12V zener is not a good idea, as was suggested here: https://www.msextra.com/forums/viewtopic.php?t=39695

 

Over time I started having a jumpy tach under load, and I think it was somehow also contributing to some ECU noise. Switching to the correct 18V zener cleaned up both issues.