HO power pack

Fixing HO or N scale electric trains that won’t move and make noise

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.

The cure is usually simple, involving switching a couple of wires.

HO/N scale power packs (sometimes called transformers, though technically they’re not) have two sets of terminals on them. 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.

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. Just swap the wires running from the track onto the other set of terminals.

HO power pack
Note the two sets of terminals on the power pack, to the left. If the train doesn’t work right, move the two wires over to the other pair.

This troubleshooting advice applies to any HO and N scale trains (except for Märklin), or any train that runs on DC for that matter. But 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.