I am in the process of restoring a '70.  I have gutted it and am in the process of putting it back together.   My next step is to install a new dash.  I have moved the dash wiring harness to the new dash along with all the gauges and I am about to plug everything back into the harness.  The engine is still out of the car.

I am about to plug a battery into the harness so I am very intimidated at the thought of burning something up.

My ground is connected correctly.

Assuming I am careful and connect the electrical components back together such as the lights, horns, etc. so that nothing is touching metal that shouldn't, I see there are 3 wires coming off the positive battery terminal.  One is a thick black wire which goes to the starter.  I assume that powers the starter motor.  Since there is no starter right now, I assume I can put that one aside.  That means there is a smaller gauge black wire going to the solenoid  and another going to the fusible link.

If I wanted to apply power to the harness to test the lights, horns, gauges and so on, is it safe to say I only need to apply power to the wire with the fusible link?

I also thought I would pull all the fuses from the fuse box except the circuit I am testing.  That should eliminate any chance of burning everything up. Agree?

Any suggestions?

Put one of these in the power supply line from the battery.  A 20 amp fuse (or 10 if you want to be really cautious) should protect any of the wires in the harness.  If it blows right away you have a short.  As you turn on various lights and gizmos and it blows you'll have a clue about which device has a problem.

The 240Z owners manuals have good wiring diagrams in them.

https://www.autozone.com/electrical-and-lighting/fuse-and-accessories/bussmann-atc-fuse-holder-with-cover/32415_0_0?spps.s=4180&cmpid=LIA:US:EN:AD:NL:1000000:ELC:71700000060662503&gclid=CjwKCAiAn7L-BRBbEiwAl9UtkHW6xyqKPANG2FaYsa9znpvCznDnG5GjjBuOLa2uPpPq0ebehc1UzBoCzqQQAvD_BwE&gclsrc=aw.ds

Edited December 6, 20204 yr by Zed Head

I think that you might have to ground the potentiometer (dash light dimmer) circuit to get the lights to work.  It might ground through the dash frame.  Gotta have a ground.

Last thing - measure resistance through the circuit from power supply to ground before you apply power and you'll know if you have a dead short before you even blow any fuses.

Edited December 6, 20204 yr by Zed Head

When I first re-connected power after my car sat in my garage for 20 years, I pulled all the fuses and connected a trickle charger instead of an actual battery. It's limited to 3 amps, so seemed pretty safe. I then added one fuse at a time and tried each circuit. Surprisingly, the 3 amps was enough to do a high level check on a lot of the circuits. Once I'd done that, I pulled all the fuses again and connected the battery and repeated the process. Prior to doing all that, I'd spent quite a bit of time at the back of the car repairing wiring that had been chewed by mice, so I was pleased to find that everything worked.