It's great to see your model trains running around the track, but if they suddenly stop, tip over or can't get started, you will have to troubleshoot the problem. Electrical issues, derailments and burned-out engines are fairly common and all tracks require maintenance now and then. But there are ways to figure out what the source of your problem is and get back on track. All you need is a little common sense, patience and a methodical approach.
Troubleshooting Electric Trains
Create a test track by hooking up a separate feeder track and a couple feet of flex track to your transformer to test engines. Place your engine on the line and add the power slowly. If the engine does not run, your problem is there. If it runs slowly, the motor may be dirty or dying out.
Wash your hands and run two fingers along the track slowly to test for rail connection issues, including glue, debris or dust on the track. If you feel bumps or gaps, inspect the track for mismatched or disconnected rails. Mixing different rail codes can cause this as well as uneven surfaces and it can account for derailments and sudden power loss.
Remove the shell of the engine and check for dust or debris in or around the motor, wheels and axles and brush away any foreign particles. This problem often accounts for poor performance, burning smells and loss of power.
Locate areas of the layout where engines seem to lose power and try adding additional feeder tracks. Power degrades as it travels the rails, so the longer the total length of track, the more electrical feeder points you will need.
Sweep out your turnouts with a small brush to clear debris and inspect for contact issues. Test to make sure the switch fully opens and closes without a train on the track. Adding a small amount of oil to the moving parts can help if the connection is stuck or inconsistent.
Inspect your wiring from underneath the layout as well as at the feeder tracks. Most wiring issues are either weak connections at the rails, or loose or damaged wiring underneath.
Check to make sure your polarity is consistent throughout the layout. The best way to be consistent is to wire all right-hand rails to the positive DC terminal with red wire and all left-hand rails to the negative DC terminal with black wire.
Replace old light-duty wires with 12 to 14 gauge wire if you continue to have power issues, especially on large layouts.
If you have derailment issues even after checking all this, it may be because the radius of your curves is too tight. Six axle engines and long rolling stock require a greater curve radius.
If you have electrical power issues after checking all this, you may have switched the AC and DC lines by accident. DC is for the train tracks and AC is for the lights and other accessories.
Do not lay anything metal, like the shaft of a screwdriver, across the tracks. It will cause a short and can damage your engines and even your power pack. Most of the relevant material from Resources can be found in the middle of the page several paragraphs into Section 2 called "The same car or engine keeps derailing."