1963 C10 with 10SI Alternator Question

[Cris]

OK. A bit confused right now. I have put in a 10SI alternator in my 1963 C10. It is wired per the many schematics on the web. I use the brown wire to the number 1 terminal to excite the alternator. The number 2 sense terminal goes to the horn relay junction, the output wire of the alternator also goes to this same junction.

Here’s where I get confused. With the key switch in the on position without the engine running, the voltage on the number 1 terminal (brown wire) is around 4 Volts.

My guess is that the brown wire connects to a brown white wire under the dash then to the ignition switch. The brown white wire is a resistance wire? I am also guessing that the alternator when not being spun is relatively low resistance at the number 1 excitation terminal. This low resistance would create current flow in the brown wire to illuminate a dash charging bulb. (My truck has a voltage gauge so no light). I’m also guessing that when the truck is started and spinning the alternator, the number 1 terminal goes up to 12V?

Any help would be appreciated, Cris