I am installing a Pertronix Digital HP box. Where can I find the 12v ignition switch wire in the engine compartment to hook up to the distributor? Anything on the relay board? Thanks. I am great with mechanical stuff, but electrical is like opening a can of worms.Click to view attachment

The AAR wire (white) on the ignition harness is switched 12V.

AAR? Aux air regulator? The only problem is I have 1.8 Let not 2.0 Djet.

On your original ignition harness that lays across the engine from the relay board to the coil, you have two wires going to the coil. Black, and black with a stripe. Black was your original coil +12V supply that is switched, and the other with the stripe is the tach signal.

Already have 2 wires coming out of the box going to the coil.

Edited my last post for clarification.

Got it! Next question, is the tach a voltage spike tach?

Original tach uses a pulse signal. You will likely need a conversion unit to take what I bet is a square wave from the box and turn it into a pulse to get the tach to work. I have MSD on my car and used their tach adapter with no issues. Not sure what part number at the moment.

Alternatively, the tach could be rebuilt with a newer drive unit that uses a square wave.

Still sorting this out. I have a 75 914 with Ljet fuel injection. Where can I connect the red wire coming from the distributor and the box to the ignition switch?Click to view attachment

Hope this helps. It's what I used on my '75 L-Jet. All works fine.

I separated the black wire from the black/red wire left the black/red wire on the + side of the coil and connected the black wire to the red wire. The wires coming off the positive side of my battery are fused. I hit the start switch and blew a fuse. ?????