Excess current in Ignition 1 circuit?

It IS possible that you have something amiss. One example might be a partially shorted alternator field winding, which does happen. (This will cause less than rated alternator full output.)

The most likely suspect, however, is the switch connector itself.

You have any added loads, upgraded ignition, etc?

And I assume you don't routinely leave the switch "in run" with the engine off?

Is there any evidence along the "run" circuit of damaged insulation or other heating?