One of the passenger cars from a Roaring Ridge set seems to have developed a short.  When the car is on the track, the engine will not run and a faint buzz can be heard from the car (at the wheels).  The interior light does not come on.

I have taken apart the trucks and put them together again and inspected the car for any obvious shorts, but no luck.  If I disconnect the trucks (either) from the black wiring, the train will run, but obviously the light does not come on.

Any suggestions for a fix?

Hope all are enjoying the holidays.

Thanks in advance,

Mike