Later 911 2.7 tacho,, wiring info anyone,please Options

[porschetub]

My current tach is from memory a 72 911 one,looks nice but that's about it,the needle is unstable as rpm changes and not reading right.
I have a later tach which is from a 76 and has 8 pins on the back (only 3 used) can anyone tell me what pins 2,5 and 6 are for ?.
1 x purple black to engine loom,
1 x brown earth,
1 x red/black switched power.
I need to know which wire to which pin,thanks in advance

[Steve]

It's not rocket science. There is a part number on the front of the tach, google it or look it up on the PET to find out for sure what year it is. Buy a 911 Haynes Manuel. It has diagrams for every year 911 up to 89. I used a 3.2 / 930 tach with both my 2.7 with webers and my current motronic 3.2. All I used was the Haynes Manuel and pet to figure it out.
Here's my notes.
91164130106 = Euro / 05 = USA = 84-89
2=blk/Purple= signal
5=Positive
6=Negative

Get the part number off of the front, so we can look it up.