Thriftair heater switch bad?

[Streetglide2015]

So during my lengthy process of elimination as to why fuses continue to blow on my '64 Chevy Thriftair heater, I have done the following, with no success:
- replaced blower motor with new unit.
- replaced resistor.

But now it seems that with both of those items replaced, the fuse only seems to blow when fan is turned to "High." It runs as long as I want on the first two lower fan speed settings, but when switched to high, the fuse will blow after a few seconds.
I'm now thinking that the switch itself could be causing the problem... It's also difficult to pull out and push in (for heat control) and is probably original.

Thoughts, advice, and comments are welcomed!