Tachometer

denbou · 02-03-2018, 06:14 AM

I had a 3.2 engine installed in my '76 911 - for some reason(s), the tachometer no longer works and the mechanic cannot figure it out ...
anyone has any idea(s)
Many thanks

JimmyT · 02-03-2018, 06:27 AM

TACH-ADAPT

denbou · 02-03-2018, 07:33 AM

Thanks - i will check this out !

Trackrash · Trackrash's Garage

How is your tach hooked up now? You went from a three pin CDI to a 6 pin CDI.

When I did this on my car I hooked the tach to the coil, worked in my case.

The six pin CDI has a connection for the tach, but not sure if your original tach will read that signal. The Carrera tach reads off the DME, I believe.

Flat6pac · 02-03-2018, 03:32 PM

The tach drive on Carrera originates in the brain.
There is an adaptor in the front brain harness with the purple stripe black wire. That’s the tach drive, jump it to the back of the tach.
Bruce

Walt Fricke · 02-12-2018, 10:59 PM

The tach signal from the DME to the tach is a nice square wave, 5V I think. It should work with your earlier tachometer, but if not, use a tach adapter on that signal. It has all the very little current needed.

Don't mess around with running a wire (or finding an unused one) from the engine up to the tach. The DME knows very accurately what the engine speed is at any given moment - that's how it adjusts spark and fuel from the throttle position and other inputs.