I have the painted version on the bench for a repair. The 2R-3R units do route both wheel sides to black power wire or Outside rails when in the 3R position. Only when the 2R-3R switch is in the 2R poisition does the wheel isolation come into play.
For this unit, the rear truck left wheels are connected to the tender chassis via metal bushings and a gray wire is routed to the polarity switch. There also is a gray wire with screw into the tender frame connected via wire nut.
The right tender wheels on the front truck are linked to the polarity switch via the wiper. They also are connected to the engine right wheels via harness. One issue is the blackened axle.
When the 3R switch is in 3R, the brown wire bringing roller power from the engine (and tender if equiped) goes directly to the PS-2 3V board red wire position.
The polarity switch (depending on which position) routes either the left or right wheels to the 3R-2R switch an directs it to the black 7pin connection.
The polarity switch sends the other wheel set to the 7pin ground connection via a direct connection from the polarity switch.
The main point being that when in 3R both left and right wheels from the tender and engine go to the outside rail position for board power.
If an engine is having problems then one of the switches, pickup points, tether wires, draw bar ground may be having issues. G
