Had a bit of excitement.  After four years got my 1970 240Z fully restored and on the road.   After about 1 hour of driving had smoke in the cab from insulation burning on one of the primary power wires under the dash (see photo).  I repaired the wire and added a new female spade connector and then proceeded to clean the connectors under the dash by the passenger kick panel (second photo) as well.  I then reconnected the wire and ran the car and held the wire with my hand and noted it becoming hot.  Tested resistance on the wires and they seem fine.  Also, noted that when I turn on any item, lights, dome light, brake light, etc. the fuse clips related to that item also get warm.  I checked all the fuses and then pulled them all except for the ignition fuse and experienced the same result; warm/hot charging wire.  The primary wire from the alternator does not get hot nor does the wire to the starter/battery.  At this point I am stumped and need some advise please.

Hi , I had the same thing in my 03/1970 240Z a long time ago . Have you checked back of the fuse box ? In my case , the two bold white wires were sticked each other in the back of the fuse box .

I replaced the white wires to the new ones and then having no trouble since then .

Kats

Yes, I pulled the fuse panel and all looks good.  Also, checked the condition of how the wires are connected to the fuse bus bars and all are tight   

What's the voltage?  You might have a bad regulator.  More volts = more current = more heat.

Zed Head, you identified part of the problem.  Voltage regulator at higher RPM was putting out too much voltage, however wires were still getting warm.  replaced all of the spade connectors on the wires and seems to have resolved the issue.  Thanks for all the help folks.