"Unless I am mistaken, the melted switch would be IG (main switch) and the lugs that are burnt out are where B (white) and M (brown) wires connect from the Ln (mains line). Is this correct?"
Very close... the melt was on IG (main switch) terminals B (white) where Ln (main line) connects and the terminal directly above where wire BR (formerly white-red) jumps to the PC switch (pump control).
Update. Cutting off about 4in of stiff and less flexible power supply cord at the switch end seemed to solve the problem. After about three weeks of pulling morning shots, it appears that I have not had any overheating at the switch. I still do not know if the increased resistance in the stiff wire caused the heat, or if another problem caused the stiff wire. In either case, I'll watch it like Corona.
Thank you all for your posts. I appreciate your help.
Equipment doesn't work? Troubleshooting? If you're handy, members can help.