Wouldn't a closed gap in what was to be a gapped loop lead to an immediate short, at least in the case where a metal tire crossing the affected gap ought to have been the cause otherwise?
When I started reading your post, the mention of 12 years of flawless performance and then a failure when returning to the layout in October makes me wonder if a gap has closed over the summer. Humidity? Whatever. Put on your Optivisor if you have one and examine the gaps to be sure that they have remained open.
Rich
Alton Junction
John, this sounds frustrating. A few questions. 1. Did you try the Hudson on the west loop? 2. Is this a first run for the Hudson through the east loop? 3. Is there a piece of equipment bridging the gaps at the other entrance/exit to the east loop? 4. Does the Hudson do this taking either path into the east loop? 5. Did you try other trains on this exact path as well in your troubleshooting? 6. Have you tried cleaning the wheels & tracks? I had a similar situation with one particular locomotive and that solved it. Other trains would run through the reversing section just fine, but this one locomotive suddenly wouldn't anymore. The system would see a short and shut down. It ran fine around the rest of the layout. Sounds frighteningly familiar to your situation.
Mike
One of the frustrating things about this hobby is that it seems something is always breaking, often something that has worked flawlessly for years and this is no exception. This is a cold weather hobby for me and I resumed around the end of October and it seems it has been one thing after another going wrong.
My layout runs on DCC with a dogbone schematic with the end loops forming a 3 track staging yard at each end. Each track can hold two long or three/four short trains. Since I am a lone wolf operator, I use a single autoreverser for both loops. I don't have to worry about trains entering/leaving the reversing sections at the same time. This has worked very well for at least a dozen years with my current autoreverser. Yesterday it stopped working.
At both ends of the layout, trains enter the loop in a counterclockwise direction. Yesterday, a Hudson tried to enter the east end loop and as soon as the drivers hit the reversing section, the system shutdown which it is programmed to do whenever there is a short. I backed it up by hand and tried again. And again. And again. Each time the system shut down. I had several trains in the east end loop and I had them exit which they did without a problem. I tried the Hudson again. Same thing. I then tried the west end loop with a single loco it worked just fine. I ran it all the way around the loop in both directions, entering and exiting the loop several times. This tells me the autoreverser is working. I can't figure out why it won't work for the east end loop. Power to the autoreverser comes from the bus line. It then passes to a distribution block which distributes power to the tracks of the staging loop. I checked all the connections with the Multi-Meter and there is plenty of juice reaching the distribution block. I checked each of the connections and they were solid.
If the autoreverser wasn't working at all I would figure it is shot but it works fine for the west end loop. Since the tracks from both loops connect to the same distribution block, electrically they are part of the same zone. The non-reversing section of the layout is divided into two zones with the east and west loops connecting to different zones but I don't know why that would matter.
Any ideas because I am out?