DCS/DCC switch wire broken on subway set

      I believe the switch connects the wires to make it  work in DCS and disconnects the 2 wires to run in DCC.  This is why it won't run in DCS. I would just solder the wire back onto the switch.  Removing the switch and wire nutting the 2 wires together should work also.

Correct, the wires closed (shorted together) is DCS mode. In fact, many Railkings come with just the jumper wire shorting for DCS mode and no switch. A wire nut or any other safe method that prevents them from shorting to anything else would work.

Again #1 golden rule- never let any wire short to frame ground or anything else.