I am really puzzled about this. I have an MTH F-7 scale A-B-A set, with very few miles on it although it's about 5 years old. I ran it for a short time about a month ago, and everything was fine. Today, I put it back on the track and as soon as I turned up the track power, the trailing A unit started to run on its own, without lights or sounds. It wants to run into the B unit that it's attached to. The more voltage I apply to the track with the Z4000, the faster it goes, ignoring the DCS system. I removed the leading A and B units, and applied power to the track and away it goes in a conventional mode according to how much power is applied to the track. I added the A and B units back on the track and hooked the trailing A unit onto them, insulating its pickups and wheels from the track by slipping a sheet of paper under the unit so it wouldn't receive any track power. When I applied power to the track again without powering up the front A and B, the rear A unit started running on the sheet of paper. I hadn't even fired up the leading A and the B unit yet with the DCS remote. I could not delete the engine from the remote because to do so the track power needed to be on, which would cause the trailing A to turn on and grind its tires away. I removed the trailing A from the track and applied power again, and the leading A and the B unit operated correctly, so I removed the engine from the remote and added it back, which was successful. However, the same problem came back when I added the trailing A unit to the track.
I checked the undercarriage of the engine for anything out of place. I removed the body and checked the internal wiring for damaged or pinched wires and looked it over for any other possible defects, but everything appears to be in place. I paid special attention to the wired connectors between the units, including the wires soldered to the pc board that the pin connector bodies are mounted to.
Any suggestions or recommendations would be appreciated. Thanks.
Mike
