Marker lights out.

Care to share the exact model number of the engine?  Is it Legacy or TMCC?  Have you tried the reset sequence specified in the manual?

This is a Lionel 6-18340 (Century Club TM-1). I have tried the reset but still no markers on either end although the head lights are working fine. The TM-2  has lighted markers as well as headlights.

Hard to say without seeing it.  It has a couple of lighting boards, but I have no reference to how they're wired.  I don't see that model in the Lionel documents, time to start tracing wires.

Tracing wires? There's a "million" of them. wiggled all plug ins, checked the bulbs, reset the engine. All to no avail. Since they are supposed to be always on, I might just get some grain of wheat bulbs,; wire them in series and hot glue them into place; and tap into primary source.

As I planned in the previous post, I have installed grain-of-wheat bulbs in the four inside corners of the engine and the effect is identical to the original lighting. This way I have not tried to alter anything else in the engine. I am obsessive about marker lights and number boards. I am supposing that in actual railroad practice these are of little concern or perhaps I am mistaken.

Take a deep breath... all can be fixed.

Reset the engine first.

Next pop the lid and trace the wires back to the board.

Cannot remember if these are a spring pad or they are connectors back to the main board.

Can you provide a pic?

Try reseating the connector...

It is always possible that all the lamps are defective. Don't like the probability of that? It's possible that the wires are all bad. Don't think that's true?  How would you go about trying to fix a lighting problem in, say, your automobile, or your kitchen?  Drill out all the lamps and glue in different ones? Or would you try to use a more methodical and intellectual method to trouble-shoot?

After I die, I hope that I will be remembered as that guy who always asked the same questions, when confronted by a fellow modeler who had an electrical problem:

"DO YOU OWN A METER?"

"DO YOU KNOW HOW TO USE IT?"

I'm an idiot!  Having said that, don't be like me. Celebrating my rebuild of the smoke unit on the FEF3 844, watching it chuff and smoke down the track, I thought wait a minute. I see only one number board lit and no classification lights. Yes on the headlight and emergency light.  Opening the shell I find six wires pinched inside the dual smoke funnel and the two shell stack openings. Two were cut in half, and four stripped of insulation at two pinch locations. The wire bundle tab had come loose and I didn't check that putting the shell back on. Took an hour for a tyro like me to straighten out. All's well now, but don't be like me.  Figure it out.