New harness problem

OK, sounds like you have a problem with the black, which should feed a buss in your fuse block, and indeed, would explain "no wipers" "no heater" or other acessories

The voltage at the coil "could be" normal, it WILL be dropped by the ballast resistor. The voltage at the "key" side of the ballast is OK

The yellow off the igntion switch only goes one place--through the bulkhead to one of the "push on" connectors at the start relay. Does not matter which.

You have an automatic? With the transmission in neutral/ park, the second "push on" connector at the start relay is grounded by the neutral safety switch at the transmission

The brown only goes one place --from the ignition switch, through the bulkhead, and to the coil+ (may physically connect to the ballast resistor) This is the circuit that gives you a "hot spark" during cranking.

Sounds to me like you are making progress.