Lionel Remote Switch Troubles

Are all the track pins, in both power and running rails, present and tight? If yes...

I suspect a cold solder joint, or a frayed wire somewhere.  I would take all the trains off the track, turn up the track power to, say, 12 volts, take a test lead and jumper each wire, in succession, until you see the lamps come on at full brightness.

Also, you might take a test lead and jumper from a known good hot track source and a known good outer rail location.

If it's a bad solder joint, hit the suspected one with the iron, and re-melt the connection. In fact, re-melt all of the ones you see, as a proactive approach.

It is a Fastrack track switch (from the pic of the remote control). There is a small resistor in the red wire that goes from the "AUX IN" terminal to the circuit board. It acts as a fuse and can fail open. Either check continuity of the wire or with power connected verify that there is voltage at the molex plug on the circuit board.

The resistor is in the black shrink-tubing at the screwdriver tip. They have been known to fail.