Thanks guys! It worked! I really appreciate it.

Take care

HI everyone, I'm new to the model train world. I have collected a few locos and just received a brand new spectrum 4-8-2 light mountain. I opened it up and the first thing I noticed was that something was rattling in the tender then the front wheel assembly came off and i realized the screw was missing. I removed the cover and located the screw and got it all back together just as the diagram shows.

Afterwards, I placed it on my track that I know works, turned the dial on my digital commander and... nothing. I tested another loco - no problem. I tested it with a new athearn dc power pack - nothing. I noticed that when I pick up the front wheels of the tender the loco begins moving but the second they touch the track everything stops except the light in the cab of the loco. In case you were wondering, the loco is not dcc equipped and is not dcc - ready at least it doesn't say so on the box. There is a wire harness that connects the tender to the loco.

Questions:1.!What does the circuit board in the tender do?
                  2. Why doesn't the loco move on its own without being attached to the tender?
                  3. How do you think I can fix the problem?