Tach Help!!!!!!

[rs92s1880]

:bang head:Bought an autometer tach that is usable down to 4 cylinders. wired in signal from 2 rear coils with diodes(facing the right way) in line prior to the junction going to the tach. it looks kinda like this

coil neg--------->l-------------+---------------------tach signal wire
coil neg--------->l-------------+


Heres the problem.

it works just feeding from one coil, albeit at half actual rpms. as soon as i hook up the second coil, the tach completely stops. ive double, triple, quadruple checked every ground, power, wire, connection i have made. i have jumpered signal with other diodes and jumpered around all of the wires in the setup.

I am using 1000 volt diodes from radio shack. i thought maybe that could be the issue, but it functions the same exact way while working off one coil whether i have the diode in-line or not.

AAAAARRRGGGHHHH!!!!

 

[Thevmaxrider]

Does your tach have the brown wire (at least with my Autometer Procycle one it is brown) that loops out of the hole the wires enter the tach body at? If so, cut that wire and tape the ends, push it back into the housing and you are cooking with gas. That wire changes the tach to accomodate the ignition system a Vmax has. Mine initially read 50% of the actual rpms until I cut that wire. No need for the diodes either.

 

[rs92s1880]

My tach is an automotive one that only allows for 4 cylinders by cuttin 2 wires in the back which puts it in 2 pulse mode, looking for 2 pulses per revolution. With one coil connected to thesignal wire, it only puts out 1 pulse per rev. If I had a procyle tach adjustable down to two cylinders, it'd work fine, hence the extra wire connecting the two coils in parallel up to the diodes, and after that they're connected to the same tach signal wire. It works fine with one coil connected (at half speed). Once I hook up the second wire the tach goes dead.

 

[naughtyG]

maybe try using different coils, like one front and one rear and see what happens?

 

[[email protected]]

I was thinking about buying a phantom, 5" monster tach with shiftlight and knew this was going to be an issue. I emailed tech support and explained the situation. They said it can be fixed inside the tach, no big deal. They said it would cost around $30 for the repairs.

I never did get to buy the thing. To email tech support go to their website and look around, you'll find it. They were pretty good with responses.

 

[rs92s1880]

Just spoke to the tech line at autometer and was told that the two coils are getting overlapping signal and getting a cancelling effect. Would a resistor work to "slow down" the signal?

 

[rs92s1880]

Oh yeah. I'm using the 1 and 3 coils that are supposedly firing 180 out

 

[vmax626]

I just bought a Sunpro 5" ttach that has a switch for 2, 4, 6, or 8 cyls. from Auto Zone
so, I set it on 2 cyl. and it works fine and at $99.00 it was a good deal too.
<<Dave>>unk:

 

[blackmax69]

Im having the same problem but am wondering if there needs to be resistors inline to smooth out the signal as the 2 coils are giving a spike effect and she locks up solid.Please help guys if you know what is up

 

[bikedave99]

:bang head:Bought an autometer tach that is usable down to 4 cylinders. wired in signal from 2 rear coils with diodes(facing the right way) in line prior to the junction going to the tach. it looks kinda like this

coil neg--------->l-------------+---------------------tach signal wire
coil neg--------->l-------------+


Heres the problem.

it works just feeding from one coil, albeit at half actual rpms. as soon as i hook up the second coil, the tach completely stops. ive double, triple, quadruple checked every ground, power, wire, connection i have made. i have jumpered signal with other diodes and jumpered around all of the wires in the setup.

I am using 1000 volt diodes from radio shack. i thought maybe that could be the issue, but it functions the same exact way while working off one coil whether i have the diode in-line or not.

AAAAARRRGGGHHHH!!!!

As an FYI, I had the same problem trying to get my Glowshift digital tach to work using the same circuit. What made it work? Flipping the diodes... I know, it doesn't make sense to me either. I found a few different places on line that corroborated the diodes facing the other way...