Jscaramella

My tach in my 1972 died. I have checked the obvious fuses, no luck
I even tried to replace the tach no luck.

The wires behind the tach lead to: Ground, 12V supply and a Black/Purple that seems to end up at what the Haynes man. calls a speed sensor?
Is the the RPM transducer locatde in the engine compartmnet?

Any ideas? Thanks. I'm a new memeber

Jscaramella

Well after no replys, I deceided to reply myself : ) in case anyone reads this.
I serched the rennlist archives and found some info on the case.
Seems in 72 the tach wire runs from the dist. to the tach to feed the info.
The 12vlt source at the tach was good as well.
With a meter I read the tach info (3-4v) and the wiring is fine.

I did purchase a new tach from DC Automotive (assuming that they test them!) and this one is also dead as is the original unit. Oh well now I have two tachs to repair.

Lovely!!!

art

I would think you would need a scope of some kind to see the tach signal.

You could try hooking up an aftermarket tach to your signal wire as a check. I'm not sure about the specififc differences on a '72, but on my '70 914-6 the tach signal is a big negative spike. I'm no expert with a scope, but that is what I found.

When I hooked up a 911 tach to my crankfire which puts out an 80v positive signal, it killed the tach, so assuming the '72 does something different you may have a compatibility issue. I ended up putting a cheap aftermarket movement into the blown 911 case and it works fine. Takes a bit of fiddling.

If you have two tachs that don't work, that may also suggest something else. Good luck!

Art