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  View original topic: 914 tach wiring
porschevw Thu Aug 25, 2011 9:26 am

I have a '74 914 and p.o "played" with the wiring to the tach. I can't seem to figure this out. Can anyone tell me how the tach is hooked up. I put a tach in my baywindow westy and all it needed (if I remember right) was power, splice into the dash lights, and run a wire to the negative side of the coil.

Thanks,
Jon

type47 Mon Aug 29, 2011 5:48 am

tach is located in track 71

http://www.pelicanparts.com/914/parts/Electrical/914_electric_74D.jpg

looks like just 2 wires; black/purple is tach signal

mtwrench540 Sun Sep 04, 2011 5:50 pm

what about ground?

boxcar Fri Aug 10, 2012 3:18 pm

It is a nice addition albeit BIG...

I am wiring up an Electromotive XDI/Cranktrigger unit.

I ran an old 914 tach before triggered off C(-)

Electomotive manual describes this "some older tachometers trigger off the high voltage signal from the ignition coil (c-). These type of tachometeters require the use of a tach amplifier....designed to trigger off a 120 volt signal."
Trying to figure out what the (-)side of the coi is putting out?

Just a 12v pulse? Or 120v as the manual describes...the FI picks up a pulse here also, and i looked but saw no test values in the EFI sticky(nice to have this!!)

Anyway, I bought an amplifier already so I am just confirming theory before i start stripping wires...thanks

mtwrench540 Fri Aug 10, 2012 4:27 pm

there only three connections that you need,#15 to ign source,#31 to ground,and last wire(i forgot #) to point side of coil,green wire!



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