wanted to hook up the stock tacho to the cadet ecu

tried ECU wire 7 (yellow with red tracer), was described as "tacho drive output" on a diagram i had and on the stock S13 wiring for the tacho it looks like wire 7 is hooked to one side and other side hooked to earth

tried wiring the 1200 tacho with wire 7 one side and earth other but didnt get any reading on tacho

so....................... how is it done?

with an aftermarket guage

or lots of #OOPS#ing around by someone that knows alot about electrical systems, and in the end you have a tacho thats not that accurate and slow to react

i always found it funny when i had the stock tacho and the autometer one in my sedan, coz im that col i needed 2 tachos, you could quite easily see the different in the readings and how much slower the stock one was to climb

i thought it was meant to be easy, bugger

to emulate the 1200 wiring style for tacho i would need to run the fat blue wire from the S13 loom (which powers coils) past the back of the tacho, dont really wanna do that

was keen to keep stock looking dash setup, and not really that fussed with what the tacho says except to set idle really

I've heard that if you run the +ve to the coil(s) through the pick up on the back of the tacho it will work. I had problems with my tacho and converted it to run off a tach voltage signal. I wound a coil on some small black water pipe, fitted it over the pick up and drove it with a bc337 through a wire wound resistor. I went for (from memory) 100 turns of the coil and 60mA to get roughly the same field strength. I uploaded some pictures and would be happy to sketch up a wiring diagram. It works running off the tach output of my hei.

I put a XE tacho into the 1200 housing, with the 1200 needle and face.

The ford tach is about the same sweep in terms of the calibration as the 1200 tacho and will run of an electric pulse. Was alot of rooting around and didnt use it anyway as was not as acurate as the vdo unit I now have.

two good options...thanks

interested in converting one for me lamb_daqs? otherwise yeah i think i would like the info

It was a bit fiddly and I'll have to remember exactly what I did. My design needs a little refinement as I ended up needing to add a heat sink which is not ideal. I'll hunt around for the schematic when I get a chance, the best bit was it's totally reversible and is a bolt on to the existing tack, there's a thread on what I did here http://datsun1200.com/modules/newbb/v ... id=291394#forumpost291394

I'd suggest a higher resistance and more winds, maybe double the winding count and double the resistor value. I calculated less than the 5W rating but it got hot and stopped working.

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tried this, test drove it today... works a treat! very happy

i just cut into the wire going to the coils (10 or 15 amp) but i used a 25amp rated wire (so that i wouldn't be adding resistance to the circuit by extending the length), by joining that in i extended the blue wire, ran it past the back of the stock tacho in the same way the original one did and then back to the other end of where i cut it, effectively extending the blue coil power wire from the S13 loom.

Nice- is it accurate?

well it works under the same principle as a timing light, it should be very accurate

i tried to notice if it was slow/laggy, but didn't really pick it up (noise vs needle movement), i know the aftermarket ones dont seem to have the same dampening as standard ones, and therefore often the aftermarket ones seem rather irratic to me