How To Find A Short On Model Train Tracks
How often do you clean your tracks?
There's a problem
I've been working on a new layout for my O Gauge trains. All of a sudden, on of the loops of track began shorting out. I couldn't figure out what had changed. I had been running test trains with multiple units and long consists and all was well. Then, all of a sudden, shorts. And not big, sparky, easy to identify shorts. Little tiny ones that you can't quite pinpoint, and you are not sure how to find, yet you know they are present.
The locos that had taken up residence on the loop were a trio of Lionel SD70's with TMCC and RailSounds. They had replaced the two Lionel Legacy Gensets that had been performing quite well. I went through several test operating sessions without issue, then, out of the blue, the locos began to act funny at various spots on the track. My first thought was that I had a problem with one of the engines. I took all three to the workbench and gave them a quick once-over, looking for wiring issues inside, dirty pickup rollers and wheels, or any problems with the trucks and couplers. I oiled and greased them and cleaned out their smoke units. Full service. I ran them on the other main line to make sure they all worked properly, and ran them as a lash-up to make sure they all worked properly together. In the mean time, I put the Gensets back on the track and tested them. They experienced the same strange behavior.
Being a tech-guy, I have a problem solving background. I can solve a problem six ways from Sunday using a dozen different "problem solving methodologies" which is great if your server room is on fire, or your computer has a "blue screen of death" but is totally useless when it comes to correcting a problem with a toy train.
I decided to attack the track first. I removed all cars from all of this circuit and disconnected all the sidings. Then, I ran one engine at a time, until I had the recreation of the same consist I was running when the problem first happened. All was well, it seemed, until I had the full train running again. Must be one of the cars, I thought. So one at a time I removed cars from the train until the problem stopped. The problem seemed to stop at an automated milk car. Logical, I thought. The car had all metal wheels and accessory-rail pickup shoes under the trucks. Maybe the shoes were causing a problem, say, accidentally touching the outside rail or inside rail at a certain point in the track. I was satisfied that I had found the problem and reattached all my accessories. I ran the new test train consist around the track a few times with no apparent problem, added the milk car to my "repair rack" and moved on, satisfied I had solved the problem.
Not so fast
Later that day, I went back to the track that had caused problems and reassembled the test consist, less the milk car, and started test operations again. After just a few passed around the track, the problems started to surface again. There was a noticeable drop in speed, the engines seemed to be struggling at random points in the track, there was no one specific spot in the track where the problems occurred, which made it hard to identify. But why did it start up all over again? The problem was with the milk car, right?
Not so much. It was time to break out the meter and check readings. Nothing. No fluctuations, consistent current all around, good continuity. Change locos again with the same string of cars. This time, three Lionel Dash-9s with TMCC and RailSounds. Wouldn't you know, same problem. So maybe it was the cars, but which ones? I went through removing the cars one at a time again until the problem stopped. This time, the last car removed was an old Weaver high-cube boxcar. There should be no reason why this car caused a short. Plastic wheels, plastic trucks, the only metal was the thumb-tack type uncoupler and that didn't come close to the third rail at all. Around in circles I went. Different engines, cars, no cars, single locos, triple headers. The only time I was getting smooth operation was when I ran one loco and just a couple of cars. Every other scenario eventually tripped the breaker on the power supply.
This left the track as being the culprit. But why? There was nothing special going on. I focused on areas where I had recently made adjustments. One in particular was a spot where I had added an automatic signal. I took the track apart and took the signal off in that area. After putting it all back together, less the signal, I was still getting the same results. I decided that since I was so focused on the track, it would be a good time to tidy up. I broke out the vacuum cleaner and cleaned all the roadbed and track surface, and the bare ares close to the track. I was picking up dust and mislaid scenery materials, and most important, I was picking up wire snippets.
I had little bits of 22 gauge wire here and there on the layout. They were scraps from wiring the switches and accessories. Hey, I never said I was a neat freak or the clean-as-you-go type. I thought about this and went back to the track section that I had just taken apart and reassembled. Part of this section incorporated two Fastrack block sections. I tool the block sections apart and cleaned them thoroughly. I also cleaned under the roadbed. My theory being that a tiny little bit of wire was stuck somewhere it shouldn't be and was causing the short.
Wouldn't you know, that did it. After everything was clean and reassembled, I ran the 3 loco lash up and fifteen cars around that track for a good thirty minutes without even so much as a stray spark. Since then, flawless operation. I can't be certain that it was a piece of wire, but something that got sucked up by the vacuum caused the problem. So lesson learned I suppose. The littlest thing, if you are not careful, can cause head scratching problems with your layout's operation. The vacuum will stay close at had for the rest of construction for sure.