Ammeter Battery overcharge

I'm not sure what brown wire you're looking at or for. A small brown wire on starter relay comes there from the neutral safety switch on trans. This wire doesn't pass through bulkhead at all.
A wire from ignition switch to starter relay is yellow.
Once upon a time a owner found a brown wire near ballast resistor which he thought was one of the 2 ignition switched wires. It turned out to be the washer pump wire which is also brown.