Sparking at starter switch

[ckulchar]

Yesterday we drove the 1931 pickup. Started four or five times without any issues. Last night when I attempted to start the vehicle to put in the garage. While holding the starting foot pedal down I only got some arcs below where the foot pedal rod connects to the starter switch.

Removed the starter this morning. Took off the starter switch and band. Bendix was free on shaft, brushes were worn about half, and starter rotated by hand easily. Cleaned the copper button on top of starter. Put the starter back together less the starter switch. Got jumper cables and clamped positive cable to bolt hole lug and touched negative cable to copper button on starter. Started spun as expected. Put the starter switch back on starter and attached to engine. Pressed the start pedal and got the same arcing as before. No attempt for the starter to rotate.

What are the symptoms of a faulty starter switch? Any other ideas?

Thanks in advance.
Charley