Start with a 1000 ohm resistor. How many bulbs will you be operating? The total current draw will affect what size resistor you need. If you are powering the bulbs pictured you'll need a good sized resistor. At least 1 watt. Do you have any specs other than 3 volts?

Thank you Lynn, I'll see what I have. It is also possible to repair many of these cracked gears. I have fixed many of them.

Here's a link to a tutorial I did.

https://tycodepot.com/thread/5710/fixing-cracked-gears

Lynn, are you able to post a link to the schematic you are looking at? I may be able to help you.

It sounds to me like it has cracked gears. They are repairable most times.

Some of the older K-4's had drivers with what I call a plastic 'hubcap'. The plastic expands over time and bulges out; rubbing on the side rods.

Pop the hubcaps out of the wheel and cut them off/out with a X-acto knife. You can then paint the metal drivers black or leave them shiny. They look kind of neat that way.

Before;

 
After;

 

I have repaired many of these problems. I clean the parts well then use super glue to hold them all together. The critical thing is making sure that the 2 wheels are 'quartered' or at 90° to each other.

Obviously be sure not to get glue all over the wheels. Best to apply the glue to the hole in the wheel then insert the axle. If you need clarification just ask.

I believe that those have a sound decoder from the factory. You have to add a DCC decoder to get them going on a DCC layout. The loco will run on an old school DC layout and have sounds.

I don't think it will ever work on your layout unless you add a decoder.

Do you have a voltmeter? Using one will quickly help you trace the wires.

Generally, the engineers side is positive. The 'right' rail is positive. The 'left' rail is negative. The standard wiring code for DCC is right rail red and left rail black.

But Bachmann (and others) have used whatever color they wanted. I have seen them use both colors together.

As for the motor, if you can figure out which pole the right rail fed, that's where you want the orange wire. Of course the gray goes to the other pole. Be sure the motor poles are not touching the frame anywhere.

wfletcher; you are getting good advice here. It also sounds like you have two problems. One is a loco that has been mis-wired and the other in a polarity problem at a turnout.

Like Trainman said with the right rail positive and the left rail negative the loco should move forward. If it does not then you need to flip the two wires feeding the motor. If that is not possible you can also turn the magnet 180°; depending on the type of motor you have.

Maybe try fixing your problems one at a time?

Northwest Short Line used to make replacement gear kits. If you carefully follow the directions they will work fine. But it is not a project for someone without some good skills.

I have made shafts from scrap sprue with a metal pin in each end.  I have also cut a section out of the middle and then used shrink tubing to splice the ends back together.

Thanks Bachmann for getting the forum back up.

https://tycodepot.com/thread/5710/fixing-cracked-gears

Regarding pulling power; have you looked at the lead and trailing truck's downward pressures? I have also seen tender drawbars that lifted the rear of the loco. But I recall you saying that this isn't the case here.

I have seen some steam locos that had too much spring, downward pressure on the lead or trailing trucks that lifted the drivers a bit.

I don't recall right off how these are made so there may be no springs at all.

How were you adding the weight to the loco?