Thanks. Removed the left and right switches, placed the right one in the left position, and put a spare of unknown ancestry in the right position. The contact, a half cylinder spot-welded to the arm, was presenting a large and varying surface area on closure. Couple of cropped microscope photographs: http://dev.laptop.org/~quozl/.2016-07-11-omron-fa/ --=20 James Cameron http://quozl.netrek.org/ --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .