i "fixed" my passenger car lighting and now it's broke...help

I would use a meter and trace the connections all the way to the light to see where the voltage loss occurs.  I would also check for an internal broken wire by connecting one lead to the center pick-up and the other end to the wire at the light connection and wiggle the wire and watch the meter for intermittent open connections.  Wires can break internally more often then you might expect.  The light wire is being flexed at the truck every time the train goes around a curve.

Good Luck...

Earl

i know the wiring connected to the bottom of the seats works.  so, it must be in the truck wiring.  there are pickups on each truck.  if it was the wiring in one of the truck, wouldn't the other side compensate?  there's not a whole lot that can go wrong between the roller and the tab that the wire slips on.  it would almost have to be a short on the wiring picked up via the wheels (ground).  if there was a short there, it may short the whole thing.  i may be seeing my issue.  how does the wiring under the seats pick up the ground from the outside rail???  there's not an extra wire coming up for the ground.

Re-assembling the passenger car may be putting pressure on a wire somewhere in the car body - causing a break in conductivity that does not occur when the car is in a disassembled state.

it's fixed.  the 2 extra wires that i thought were for testing were supposed to be connected to the screw on each truck.  i looped a wire around each screw and attached it to the wire flopping around.  since i had it apart, i decided to glue some people in the car.  looks a lot better.  lessons were learned on this project.