Tacho connection to dash

[Mordred]

If you have the test socket in the engine bay you can link two of the pins and have the sense wire for the coil appear in the 8 way connector above the fuse box. Link pin 13 and 5 in the connector with a piece of wire making sure the grey/green is connected at the coil. In the 8 way above the fuse box there is a blue white that doesn’t have a matching wire leaving (used for the rear window defogger circuit which isn’t fitted in Aus cars) and you can link to that and take it to the tacho. All other wires should connect locally. Saves running another wire to the rear. 

Adrian

[Doob]

Top idea Adrian 
A few years ago I became curious about this VW Diagnostic / Network socket in the engine bay.
I came across this interesting website (part of Speedy Jim's website)
http://www.nls.net/mp/volks/htm/plug.htm
Click on the blue dots to get wiring diagrams.

I then tried to trace the actual wiring to the plug on my 1971 Kombi.
See the attached pdf file with a table indicating the plug wiring I found on my 1971 Bus.
It was very close to the website - few minor differences. 

I do not think I have a connection on terminal #5 (defroster relay) - but I think terminal #9 has a red wire going to Fuse #2.
This table was done a while ago, I would need to double check.  

I had contemplated rigging up a remote starting switch that I could plug into this Diagnostic / Network socket- to start and stop the engine at the engine bay.
Would be handy when tuning carburetors and doing ignition timing etc.. 
Has anyone ever done this ?
Cheers Grant.

[Tintop]

I had contemplated rigging up a remote starting switch that I could plug into this Diagnostic / Network socket- to start and stop the engine at the engine bay.
Would be handy when tuning carburetors and doing ignition timing etc.. 
Has anyone ever done this ?

I've never checked which wires are still connected to my diagnostic socket...but yeah, you could easily refine the temporary setup I use. One switched jumper wire to the coil and another fused and switched (push button) wire to the starter solenoid

would definitely be easier to have a permanent setup via the diagnostic socket if you know the appropriate wires are there

Here's the starter solenoid half of the setup .. the other half is in use elsewhere

   

[Mordred]

The defroster relay connection is one of the few to go up the front and is good because the current draw with the tacho pulse is very low.  You would need to use it to run a relay to do starter work as the voltage drop would be too high over that distance but I like your thinking.  The other way is to run a trailer cable front to back and you get 7 cores you can parallel to get greater current capacity. 

The 8 pin connector has a wire on only one side and I just added a connector to use it.  I just used the little ringed numbers on the wiring diagram in the Bentley to work out where the pins connected to.

Adrian