Last Updated on December 4, 2022 by Dave Farquhar
A common problem with HO, N, and other scales of electric train that run on DC power is that when you put them on the track, they light up but don’t move and instead make a weird noise. If your model train won’t move, I can tell you how to fix it. Here are my tricks for model train locomotive troubleshooting.
The cure is usually simple, involving switching a couple of wires.
What’s that noise when your model train won’t move?
The loud, obnoxious noise the train makes is the tip-off about what’s going on. The train is getting the wrong kind of electricity.
HO/N scale power packs (sometimes called transformers, though technically they’re not) have two sets of terminals on them. The terminals look like regular Philips-head screws. One set of terminals provides DC power intended to run the trains. The other set of terminals usually provides AC power, intended for lights and accessories on the layout.
The difference between AC and DC is that DC never changes polarity on its own. The switch on the power pack that changes the train’s direction reverses the polarity. AC, on the other hand, changes polarity 50 or 60 times per second. A motor has to be designed differently to run on AC.
Why use a DC motor instead of AC? It provides a really cheap way to be able to change the train’s direction.
If you connect that second set of posts intended for accessories to the track, the engine gets AC instead of DC, and the motor just sits there, flipping between forward and reverse 50 or 60 times per second. That’s why it makes terrible noises and doesn’t move. The train still lights up because the light bulb inside it runs just as happily on AC as it does on DC.
Connect the track to the DC posts instead of AC, and the train will work properly. So the fix ends up being rather easy when your model train won’t move. Just swap the wires running from the track onto the other set of terminals. This will get your train running more than 99% of the time.
Model train locomotive troubleshooting when the problem isn’t AC voltage
If you’re using the DC posts on your power pack and your model train won’t move still, the problem is likely dirty wheels or track. Yes, part of model train locomotive troubleshooting is being a bit of a neat freak.
Try cleaning the wheels on your locomotive with some isopropyl alcohol until they’re shiny again. Then do the same for one section of track as a test. If you have older track made of brass, try rubbing a pencil eraser across the top of the two rails as well. It doesn’t have to gleam, but brass track needs to be clean and free of oxide to work well.
Once the wheels and one section of track are clean, try putting the engine back on that track section and turn on the power. If it works, clean the rest of your track.
I use a product called No Ox ID A Special on my track, which keeps me from having to clean it again and again. I run vintage O gauge trains but I learned the trick from HO and N scalers.
Other types of model train troubleshooting
This model train troubleshooting advice applies to any HO and N scale trains (except for Märklin), or any train that runs on DC for that matter. Major manufacturers of HO and N scale trains include Athearn, Altas, Bachmann, Life-Like, Mantua, and Model Power. One notable name from the past is Tyco.
Larger vintage Lionel, American Flyer, and Marx electric trains, which were widely popular in the 1950s, are a bit different. Here are my tips for fixing those.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.