Tach won't work after converting to electronic ignition

[jon8christine]

So I converted from points to an electronic ignition on my 1976 1800 as part of an engine build. After I got the engine back in the car and running I noticed the tachometer wasn't working. Every once in a while it would bounce a little, but for the most part it just sat on 0. I pulled the dash apart to make sure I had good continuity of the brown wire from the coil negative to the tach, and it was good. I read on the Mirafiori site that when installing an electronic distributor you needed to add a 0.68uF 400v capacitor in line with the brown wire. I asked Vick Auto, where I bought the electronic dizzy from, and they said no, that you didn't need to add one. I tried everything else and finally bought a 10 pack from China anyway. Just temporarily added it in line today and bam, working tach just like it should be 100%. Figured I'd share here in case anyone else has the same problem. Thanks Mirafiori.

https://www.mirafiori.com/faq/content/t ... achfix.htm

https://drive.google.com/file/d/1Pnfoxn ... p=drivesdk

[Tcamp]

I did same thing bought one on line and bam yes 100% Was worried because i watch tach more than speedo /great info!

[18Fiatsandcounting]

Yep, the original Fiat tach is expecting a sawtooth wave pattern for its input. Like from points. An electronic ignition gives more of a pulse waveform, so the tach doesn't quite know what to do with that. So it sits there stubbornly on zero. Durn its misbegotten hide...! But, the capacitor is your friend and usually solves the problem as you found out.

And lest you think I'm anthropomorphizing the ignition system, well, let's just say that my computer agrees with me!

-Bryan